Any chance to run GTA IV

you can run it, but not at any good resolution
your mainly hampered by your video card...
if you put your resolution anywhere near the console's then you'll have a pretty slide show, and not a playable video game

GTA IV is not optimized very well.

I've read posts where people with GTX 260 or GTX 280 SLI setup are sometimes experiencing very low frame rates (less than 20) when standing still.

+1 cappster (everything but the generosity)

You will be able to run but at very low settings. I have a friend with socket 478 P4 2.8( don't know exact model) 2 GB DDR 400MHz and AGP 7600 GS 256 and he can run it. Buy the way he runs it all like Crysis, NFS Undercover ect. But that is is very low settings and like 600x800 or something and it does look loke s**t and lag sometimes but he don't care about the looks. Buy the way he have finally decided to get a new sytem and I have already ordered E2220, 4GB DDR2, HD 4830 for him. He will reuse HDD's and I am selling him unneeded for me case with P5NE SLI, 600W OCZ psu and DVD-RW cheaply.

@ainarssems in my opinion (i stress!) running a modern title at 600x800 with min settings is not running it properly, therefore (again my opinion) he cannot play these titles.
You may as well wear an eyepatch, or only use one hand - it handicaps the experience and you are not enjoying the game as the devs wanted.

Depends on your budget. If you can afford I7 then wait for Phenom 2 which hits in the new year.
If you want something that does a fine job without being bleeding edge, a Q9450 build is fine, with a 4870, 4GB RAM on the above board.
Dont just go for the cheapest 4870, look at reviews for each manufacturer. Mine is a Powercolor card and it rocks (4850 though, but good manufacturer).

Thats a big cooler.

I am of the opinion that you should only really seek aftermarket coolers if stock doesnt work out. Of course you have to guage your new setup correctly and be careful with overclocks, but i do not see the point in spending money if you do not have to.

to sum this all up...you could play it but not very well nor enjoyably

just wait till ur future system