Budget Gaming Laptop

Hi there, im new here so hello everyone and thanks for helping.
My current laptop is a Dell xps m1530, core 2 duo 2,1Ghz, 4gb ram 667mhz, Nvidia 8600m GT.
I want a new laptop that can give me at least 20% more performance.
I have 1200$ top, here are my choices.
Dell, Asus, Alienware.

Dell xps Studio 16, core i5 520M 2,4Ghz, 4gb ram 1333mhz, Ati HD 5730
Dell Studio XPS 16 Laptop Details | Dell

Alienware M11x , core i5 520UM 1,3Ghz, 4gb ram 800mhz, Nvidia GT335
Alienware M11x Laptop Details | Dell

Asus G51-x3 , i5-430M Processor 2.26 4gb ram 1066mhz , Nvidia GTS 360m
Amazon.com: ASUS Republic of Gamers G51JX-X3 15.6-Inch Gaming Laptop (Blue): Computer & Accessories

Aus N61JQ-A1, i7-720QM Processor 1.6GHz, 4gb ram dd3 1066mhz, ATI 5730,

Buy now or wait, thanks