For your price you can get a very nice system. I would suggest not skimping much just because you'll get more years out of it that way. So for specs:
Processor: 2.4Ghz Core 2 Duo or better
Hard Drive: 200gb or greater 5400rpm or more.
RAM: 4GB
Video Card: 512mb DDR3 Dedicated or 1024mb DDR2 dedicated (ex. ATI Radeon HD 3650)
Screen Size: I wouldn't go bigger than 15.4 Wide screen because of portability.
Now a system with the above specs would probably game fairly well (depending on which video card you get). However eventually its gaming capabilities will fade and you'll be glad you got that extra OOMPH in it.
Here's a couple laptops to look at:
Asus:
http://www.newegg.com/Product/Product.aspx?Item=N82E16834220307R
Asus:
http://www.newegg.com/Product/Product.aspx?Item=N82E16834220308
Asus:
http://www.newegg.com/Product/Product.aspx?Item=N82E16834220279
All of the above come with a 2 year parts and Labor Warranty and 1 Year Accidental Damage Coverage.
My friend has the m50SA-x1 very nice looking and very snappy. Also it has login by face recognition which is kind of cool.