Quick question: I can run SC2 at mostly high graphics completely fine, and I heard the D3 engine is relatively the same, so do you think I can run D3 at good-high graphics while still maintaining good fps?
Radeon HD 5770 GPU
Quad Core Phenom II
4 gb RAM
From their supported graphics card list 5770 falls under high, so I'm guessing you'd get a decent frame rate. However I've seen some youtube footage of D3 beta with a 550ti which blizzard have also listed in the high category but the frame rate dropped significantly during a screen full of action.
What you tend to see is that multiplayer games gain more benefit from RAM and HD speeds than processor power or GFX card. This is due to the fact that it's often not the graphics that needs a lot of processing, or the calculations of objects, but it's rather about being able to quickly store and generate all these objects that pop-up in your screen, throwing deadly shit at you.
This is especially true when you only suffer fps-lag when there's lots of mobs filling your screen, while having fps-lag when you see bright light, or just in general having lots of fps-lag even when you are alone, is a clear indication of issues with your gfx card.
Extra note: It's quite obvious that the overall performance is as good as the weakest link in your system.
Processor speed might be important. An overclocked CPU running at 4.0GHZ might get much better results than something at 3.0GHZ.
I think my CPU is clocking at about 3.5Ghz using stock fan, I don't wanna try overclocking with a stock fan. Under the highest stress, I've seen my CPU at about 53-55 degrees (SWTOR while doing Illum).