They all suck! look for something that has a GT640 or an HD 7670 at LEAST! The second number needs to be bigger. The bigger the better.
For 900 ish you can get a Lenovo Y500 with a GT650.
The topic has already been discussed at
http://lebgeeks.com/forums/viewtopic.php?id=11734
Also, out of those choices, I would get the one with the GT630M. It's slightly faster than the 540M. But don't expect to run games at high or ultra settings on that thing..