hopkiller :
Im just making sure that my system is running properly because i just upgraded to it. Is it common for me to get low FPS in GTA IV max settings, because I am getting like 38 FPS in benchmark, and it seems to lag in game.
Dont stress yourself over GTA 4. Its so poorly optimized for PC. When it came out, people with top end systems could mostly play the game on medium settings only. Rockstar then released some statement to try and cover things up by saying that 'high settings were for future use when better hardware is out'. As if people wait 12 months after a game is released and then play it!!
I get about 65 FPS on GTA 4 with a 5870. Im guessing that your CPU could be holding things back a bit in GTA 4, but i could be wrong??
On the console versions of GTA 4, (xbox 360 and ps3), the average FPS is around 30 i think, so if 38 isn't bothering you visually (which im guessing it shouldn't) then you don't really have anything to worry about.
Run benchmarks in some other games and post your results maybe??
I think your PC is running perfectly though. As jay2tall said, in game performance is really all that matters.