Well, The Dell alienware is a very good option, but id go for the Dell Xps because of the price. In what you get for an alienware for 4000$ you can have it in the Xps for 2500$, so visit Dell.ca and check out the Dell xps, customize it. Put good RAM in it, good processor ( id suggest i5 or i7 ) and a decent video card. Nvidia 2gb video card.
I hope it helped!
-Poolpo