CPU: AMD Phenom II x2 545 (~3.0GHz)
RAM: 4gb DDR2 1066
GPU: ATI Radeon HD5770
PSU: OCZ 500w
WoW: High (AA 2x, shadows and SSAO Low/Disabled)
I was fairly happy with my pc all through cata, I had roughly 60fps throughout most gameplay (dropping ~35fps when raiding). I know this is a lowend pc but I dont have the money to upgrade everything so my question is this; in terms of WoW performance in raids, what is the weakest part of my PC and what one thing will give best value for money in terms of upgrade?
WoW is pretty much the only game I play on it and rest is just for browsing. Thanks in advance.
Ram, CPU, mobo combo upgrade to something in the second gen Intel or First gen if you have the cash. If all you do is play WoW then a GPU won't necessarily be a major upgrade until you play other games. But the 660ti or a 7850 are both good. Also, getting a monitor with 1920x1080 (1200 for more cash) would be a good upgrade as well. If your PSU is a few years old too you might want to consider getting a new one as power degradation takes it's toll and while won't hamper you being able to plug things in and play you never want to skimp on a PSU where it can kill $1000 worth of new equipment.
Your build is fairly well-balanced. If I was to point at something it would be the CPU (HD5770 is enough for the resolution you're running), it's the only thing that will help increase your performance in 25man raids because raids are almost always CPU-capped in almost every system.
But changing CPU would imply changing the mobo/RAM as well. So as Valiea said, see if you can find a cpu/mobo/RAM combo involving a Sandy Bridge (or Ivy Bridge if you can afford it) i3 or i5. Just the locked versions using H61/H77 motherboards, you can find really good deals for those.
As for CatBeef's SSD idea, well that goes without sayinig really, SSD's are heavenly...but they won't increase your framerates at all (only shorten loading times) and framerates appear to be your primary concern.
Which country do you live in, maybe we could find something?