I made 2 selections : mid end and high end. Especially the mid end one might be confusing considering the price tag of $600 which is not bad for a gaming rig but still not cheap for a desktop PC. The logic for this selection is going as cheap as possible without sacrificing huge drops in performance or quality. One could very easely take cheaper parts but is it worth saving 15 dollars for 20% less performance? This will play any current game you throw at it without any issues (skyrim/battlefield 3 etc) if you can accept not to run it at 8xAA or max settings, though high settings it should be able to manage easely, WoW will play smooth as butter on max settings of course.
The high end is just that, best parts out there without paying a single buck too much for useless features. Will play any game max settings, even crysis!
Below i will list not only the parts but also a brief explination why i picked those, so you feel confident you are buying the right parts and know why.
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Mid End
Processor :$130 AMD FX-6300 FX-Series Six-Core http://www.amazon.com/AMD-FX-Series-...ywords=fx+6300
CPU cooler : $20 Cooler Master Hyper TX3 - CPU Cooler http://www.amazon.com/Cooler-Master-...dp/B0028Y4S9K/
Memory : $60 Corsair Vengeance 8 GB ( 2 x 4 GB ) DDR3 1600 MHz http://www.amazon.com/Corsair-Vengea...Vengeance+8+GB
Mainboard : $85 ASRock 970 EXTREME3 www.amazon.com/ASRock-970-EXTREME3-SB950-DDR3/dp/B005POPRG8/
Videocard : $150 Sapphire Radeon HD 7790 OC 1GB DDR5 www.amazon.com/Sapphire-DL-DVI-I-DL-DVI-D-PCI-Express-11210-01-20G/dp/B00BWHIOQC/
Storage : $100 Samsung 840 Series 2.5 inch 120GB www.amazon.com/Samsung-120GB-internal-Solid-MZ-7TD120BW/dp/B009NHAF06/
Powersupply :$55 Corsair Builder Series CX 500 Watt ATX/EPS 80 PLUS Bronze www.amazon.com/Corsair-Builder-Watt-EPS*-CX500/dp/B0092ML0MY/
DVD rom : $20 LG Electronics 24X SATA Super-Multi DVD http://www.amazon.com/LG-Electronics...dp/B009F1DYF8/
Case : $50 Rosewill Black Gaming ATX Mid Tower http://www.amazon.com/Rosewill-Black...dp/B003YVJJ5Y/
Total = $670
Optional :
Better Videocard : $195 Gigabyte AMD Radeon HD 7870 2 GB GDDR5 http://www.amazon.com/Gigabyte-mini-...dp/B007PJTNYS/
Additional Harddrive : $100 WD Green 2 TB Desktop Hard Drive: 3.5 http://www.amazon.com/WD-Green-Deskt...dp/B008YAHW6I/
Equivalent Nvidia videocard : $150 EVGA GeForce GTX 650 Ti www.amazon.com/EVGA-GeForce-Dual-Link-Graphics-01G-P4-3652-KR/dp/B009KUT3UY/
The cpu is an AMD six core, a bargain at 130 dollars and is unlocked for easy overclocking.
I included a custom cpu cooler, unless you are really strapped for the $20i would strongly advice to buy it. All the other parts like videocard and PSU are very silent so it would be a shame having the CPU fan making itself noticeable while doing important work on the PC. And there is no way around it once you decide to overclock the cpu.
Memory over the past years has become so fast and so cheap its such a no brainer to pick RAM these days. 8GB is all you will ever need unless you run photoshop while editing a video while playing wow. you can go higher clockwise but it makes so little difference in real world applications, any money spent on performance increase is better spend elsewhere.
The 7790 is a new GPU by AMD, comes factory overclocked the the Sapphire edition comes with the best cooler in the series. Low power of course.
As storage we gonna install a 128GB SSD. You could probably save a few bucks and buy a standard harddrive but anyone who ever worked with a SSD is never going back. SSD is about 5 times faster, no seek times, no noise, low power. Now you might think its only 128GB, its really not bad. Windows install will take around 30GB at the most, WoW will take 22GB which leaves rooms for a few more games and your music collection. Also these days so many people use external drives and USB sticks.
Powersupply is where people try to save money at and often overestimate at the same time how much wattage they require. 500watts is all you ever need, no need for more. The money saved it better spend on the 80 plus bronze standard. this means the powersupply will be more effective at turning power from your socket into lower voltages that your components can use. This results in lower power usage which means lower electricity bill and lower heat giving off less heat at the same time so the fan doesnt have to spin at a higher rpm to cool it. Overall this means higher quality parts are used so the chances are lower it will catch fire or fry your parts.
DVDROM is something we can almost do without these days, lucky its dirtcheap so we add it anyway.
The case does everything you need it to do , lot of space, easy to install components.
Optionally i listed a better videocard and the nvidia equivalent of the original videocard if you prefer another brand. Should you have a huge movie collection i added a 2TB drive.
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High End:
Processor : $210 Intel Core i5-3570K Quad-Core Processor 3.4 GHz http://www.amazon.com/Intel-Core-i5-...dp/B007SZ0E1K/
CPU cooler : $80 Noctua 6 Dual Heatpipe with 140mm/120mm http://www.amazon.com/Noctua-Heatpip...dp/B002VKVZ1A/
Memory : $60 Corsair Vengeance 8 GB ( 2 x 4 GB ) DDR3 1600 MHz http://www.amazon.com/Corsair-Vengea...Vengeance+8+GB
Mainboard : $205 MSI Z77 MPOWER www.amazon.com/MSI-Computer-Corp-Motherboard-Intel/dp/B0090Z39EA/
Videocard : $250 Gigabyte AMD Radeon HD 7870 2 GB GDDR5 www.amazon.com/Gigabyte-Mini-Displayport-PCI-Express-Graphic-GV-R787OC-2GD/dp/B007PJVB3Y/
Storage 1 : $170 Samsung 840 Series (SSD) 250 GB www.amazon.com/Samsung-MZ-7TD250BW-Solid-State-2-5-Inch/dp/B009NHAEXE/
Storage 2 : $100 WD Green 2 TB Desktop Hard Drive: 3.5 http://www.amazon.com/WD-Green-Deskt...dp/B008YAHW6I/
Powersupply : $150 Corsair AX 750 Watt Modular 80 PLUS Gold www.amazon.com/Corsair-Professional-Watt-Modular-AX750/dp/B003PJ6QWE/
DVD rom : $20 LG Electronics 24X SATA Super-Multi DVDhttp://www.amazon.com/LG-Electronics...dp/B009F1DYF8/
Case : $60 Zalman Z11 Plus - mid tower - ATX http://www.amazon.com/Zalman-Z11-Plu...dp/B007M4VALU/
Total = $1305
Optional :
Better videocard : $400 Gigabyte Radeon HD 7970 OC 3GB GDDR5 www.amazon.com/Gigabyte-Radeon-Mini-Displayport-Graphics-GV-R797OC-3GD/dp/B00752QYLK/
non OC mainboard : $135 ASRock Motherboard Z77 EXTREME4 http://www.amazon.com/LGA1155-CrossF...dp/B007KTY4A6/
Equivalent Nvidia videocard : $290 MSI GTX 660 Ti Power Edition http://www.amazon.com/MSI-Overvoltag...dp/B008SBX6GI/
The intel core i5 simply the best gaming CPU out there at the moment, do not waste money on anything more expensive as games dont use more cores. Cooler wise noctua is the best air cooling out there, but at that price point there is alot of choice , i personally own this one and never crossed my mind to get watercooling. Memory is again 8GB, dont need more speed or bigger size. Mainboard is one of the best out there, while you can go way more expensive this one is for me the best overclocker out there. IT has 12+4 phases, this is the most important spec to see how well it can overclock in theory. Standard mainboards have 4+1 or 8+2. And it has all the features you could wish for. The 7870 videocard is the top price/quality card on the market at the moment in my opinion, comes factory overclocked and a massive 3 fan cooler. storage wise we are going for the same brand and type of SSD but double in size, also by default we gonna add the 2TB drive. The power supply is 750watt 80 plus gold, being even higher quality and wastes less power than the 80 plus bronze one while running any possible single videocard setup out there. Case wise im surprised how cheap quality cases have become, you cant really go wrong anymore and sky is the limit choice wise, pick whatever you think looks good in your opinion, check the reviews and you have a winner any in case.
Option i added a better videocard and the Nvidia equivalent. would you not be into overclocking your CPU you can grab the Asrock one, it has 8+2 phases so it will run cool and even overclock not that bad but spec wise its quite a difference, but $70 can matter even at that price point.
I didnt add a soundcard to any of the above rigs even as option. The Realtek 898 onboard soundchip is very very good, to the point where i cant tell anyone its worth to shed out 100 bucks for a dedicated soundcard. I personally own an ASUS essence STX and while i can tell the difference i can only advise you to buy a soundcard if you need features like ASIO or headphone amplifier.
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While its not a definite list by far, you cant go wrong. You can get 50 sidegrades for some of the components, so see this as a starting point. You might have a certain cpu and videocard in mind but had no clue what PSU to pick so this could help you also. Keyboard/mouse is impossible to give a "right" answer cause everyone loves or hates the same mouse at the same time, looking around, go to a shop to actually try them out is what i advice.
If you got questions you can ask me in this thread or PM me, also if you have a different budget we can edit the current setups to fit those, also anyone can copy paste anything of the above and post it anywhere else and take credit for it, as long as it helps people out there choosing the right parts. Or edit the above and post your own choices below. This might cut down on the "what gaming rig should i buy?" threads.
Happy gaming!