I'm currently in the process of putting together a system for me and my old system is even weaker than the OP one's.
I'l just post the setup I'm planing on putting together and a few comments on why I chose this setup.
My new Setup will most likely look like this:
HDD: 1 x Seagate Barracuda 7200.14 500GB, SATA 6Gb/s (ST500DM002)
SSD: 1 x Samsung SSD 840 Series 120GB, 2.5", SATA 6Gb/s (MZ-7TD120BW)
CPU: 1 x Intel Core i5-3470, 4x 3.20GHz, boxed (BX80637I53470)
RAM: 1 x G.Skill DIMM Kit 8GB PC3-10667U CL9-9-9-24 (DDR3-1333) (F3-10600CL9D-8GBNT)
GPU: 1 x Sapphire Radeon HD 7850, 1GB GDDR5, 2x DVI, HDMI, DisplayPort, lite retail (11200-16-20G)
Mainboard: 1 x ASUS P8B75-M LX, B75 (dual PC3-12800U DDR3) (90-MIBJ20-G0EAY0KZ)
DVD: 1 x Samsung SH-224BB, SATA, retail (RSMS)
Case-Fan:1 x Scythe Slip Stream 120 800rpm (SY1225SL12L)
CPU-Cooler: 1 x Scythe Katana 4 (SCKTN-4000)
Case: 1 x BitFenix Merc Beta (BFC-MRC-100-KKX2-RP)
PSU: 1 x Thermaltake Germany Series Hamburg 530W ATX 2.3 (W0392RE)
I'm currently thinking avout spending a bit more and getting
1 x XFX Radeon HD 7870 GHz Edition 1000M Double Dissipation Edition, 2GB GDDR5, 2x DVI, HDMI, 2x Mini DisplayPort (FX-787A-CDFC)
(European here so the prices in the links are in euro, should be around 500$ to 600$ and you should ba able to find the components or similar ones on for example newegg)
- I opted for an Intel i5 CPU as those are a bit more powerful for gaming due to most games only using 2 to 4 cores and Intel CPUs having more IPC (Instructions per Cycle) giving them more operations per second even with a lower clock rate compared to similar AMD CPUs.
Originaly I opted for the i5 3570 but was convinced that the i5 3470 is just as powerful for games, but is slightly cheaper.
- the mainboard is in µATX giving me a smaller board with less slots for cards, but as everything I need (LAN, Sound ...) does not need an extra card, I don't care and µATX boards are normally cheaper than ATX ones. B75 chipset, as I just don't need the utilities a Z77 chipset brings (I don't intend to overclock anything, for ex.).
- DDR3-1333 RAm instead of DDR3-1600 as it is cheaper and the difference is not noticeable in gaming. But with the shifting prices 1600s RAM my be cheaper next week so I'll go with what has the best price when I order.
- the 120GB Samsung SSD is for the operating System and frequently used programs (as for ex. WoW). I found only tests saying how good the 830 and 840 series of Samsung are.
- As said I am a bit unsure about the graphics card. My budget opts for the 7850 one but the 7870 one is clearly better (having not only the stronger GPU but alos 1GB more VRAM) for only about 50€ (~38$) more so I do consider it. If I had more money to blow I would for sure get a stronger GPU.