What kind of gaming will you be into? Apart from the price range, is there any other condition you want fulfilled? Screen size? Wireless connectivity? Specific game o benchmark score?
The processor on the Alienware in the above post is old technology, in my opinion.
I'd also take a look at http://www.killernotebooks.com/
(haven't bought from Mark yet, but looking into it; great performance notebooks and best customer support I've heard of, before and after purchase).