someof the best gaming laptops for a reasonable price are made by origin(yes...origin are not that bad) and MSI. MSI make a huge variety of gaming laptops for good value. However origin is more limited, here is origins gaming laptops: http/www.originpc.com/gaming/laptops/ they are actually about your budget, might be worth considering.
I would argue that laptops are not great for gaming except when necessary. The heat they generate is pretty fierce and that reduces the overall life of the system. That's my personal recommendation at least.
I had/have the M15x which came out in 2005, And even that was Pretty fast Especially when i upgraded it to a Gtx 560m.
The Alienware M1*x Laptops are Superfast and easily upgradable.
The M17x Might be a bit above your budget but depends where you live (In the Uk its more expensive because Currency Translation is non-existent practically.
I don't care what anyone says.... DON'T GET ALIENWARE!!!!!!
Same laptop as the one XtremeAero linked, I believe, except with a 256GB SSD instead of 1TB HDD and for $75 less. You can also consider saving $131 by changing to the R9 M290X and selecting the instant $50 off. A pretty minor downgrade for that much savings. That laptop is 17.3", though. In fact, most of the laptops people are linking in this thread are 17.3".