Originally Posted by Mr.Cigar
It's not really an overkill. Last time I tried GTAIV @ that res with 460 hawk and I got about 25FPS avg with shadow pushed max.
But you should get a new monitor, may be 1680 or 1920, as game does look better at higher res (Especially texture). Most game I've tried ran flawlessly @1920x1200, except Crysis Warhead (ran pretty good @1680x1050, Enthusiast).
Hope this helps.
You have to remember, however, that GTA IV is extremely CPU intensive. If you don't have a highly clocked CPU, your FPS is going to suffer.
As for the 460 being overkill, I don't think it is. It is going to push all of the newer titles nicely with good in game FPS. On top of that, it is going to give you a bit of futureproofing.
If I may ask a question though, what is your budget?
Also, could you please fill out your "System Info" under the User CP section so that we can see what your system currently looks like?