I have almost the same card (EVGA instead) and it looks like that would be the bottleneck in your system with games, since you have a quad core CPU and plenty of RAM.
I haven't done too much research but the 5750s look good to me. Unfortunately I have never used an ATI card. The first one I tried looked comparable to the 9800GT I replaced it with, because I never got it to work. After dealing with no phone support and having to wait to RMA the ATI card I decided to just buy another NVIDIA locally, because I was tired of waiting. I might have still tried ATI but the local store didn't have the ATI card I wanted.
The downside of that was I had to pay about $50 more, but at least if I had anymore problems I could just take it back to the store. I wish had the chance to try it out because it had good reviews. I edited this because I realize I was incorrect on some of my ATI numbers after looking at reviews again.
I can play GTA IV but the frame rates are really low. I suppose the CPU/memory could be affecting performance in my case but considering graphic detail is almost all the way on low I suspect the card.
I have to upgrade my motherboard to get a faster CPU so I was going to try to keep this card a little while when I do so. I'm curious to know what games you are playing now and how the performance is?
Edited by SpaceInvader75, 18 February 2010 - 05:09 AM.