If you're going to be playing any newer games, you're definently going to need more then 512, I'd say at least one gig. Pretty much any new games will require at least 4x and 512, recommended. I'd say your price will probably be at least 1200.
Awhile back I was helping a friend look at laptops, he checked out a gaming laptop and the price was somewhere around 1400, and the specs weren't that bad.
But since you're going to be buying a laptop before vista come out, make sure you get high-end and widely supported hardware to ensure that vista drivers will be compiled for your hardware.
But as Mike said, it's best not to jump the gun and wait for Vista first.