If you'll be gaming on a 650m, you're better off buying the laptop with a 720p monitor since you'll have a higher chance of maxing out visual quality (thus the game will look better) and getting better frames than compared to what you'll get with 1080p, which will be lower visual settings if you want a high frame rate. Also, if you use a non native resolution you'll have to deal with downscaling and it can look fugly as hell.
For the price I would suggest Lenovo and Asus which will probably save you a couple of hundred dollars. Alienware don't make bad PC's, they just cost a hell of a lot more than they should.