I use a Dell XPS 17 and it cost me 1600$ and i run GTAIV fine, i have a little texture loss here and there and some lag but it is just fine, The guy who i bought it from got me 50% off. My dad knows him, so i got 50%, i can get you the link, PM me if you want more info. I also got a great videocard driver and a nive 6GB in ram, and a few GB's here and there, I have like 23 games installed and i still have 5.90 useable. from having GTAIV EFLC MW3 MW2 Black Ops and some others.
Link to get how much and config your laptop to get top notch software, and other things, i have a light up keybord HD screen webcam and etc link: http://www.dell.com/us/p/laptops?~ck=mn#!facets=58106~0~1053922,133614~0~4774326,51795~0~11384532,135390~0~6687268,55846~0~5930681,52176~0~817062&p=1