I got the perfect choice in that price range: Gateway 7811-fx.
This computer is about 3 years old but came fully loaded with a good 1080p screen and graphics card. By no means is it light as it is a 17in laptop that weighs roughly 10 lbs. Basically, it will still be on par or outperform any of the smaller gaming laptops (e.g. Alienware m11x) or higher multimedia laptops (HP Envy, etc...). It definately outperforms the m11x, even though it is a couple years old. To be honest, the Gateway 7811-fx is pretty much the laptop that started the whole "gaming laptop" division with its first iterations. Since then the "gaming" laptop category has gotten more robust and pricey as well.
But there is some added risk, as they do not sell these new anymore. You will have to find it used or possibly refurbished. The going price of these machines is $600 or less. I've even seen them sell for around $400 at times. Search on google and go to a laptop forum called "Notebook Review Forum". Occassionally, these laptop geeks will sell their old rig and usually in prestine condition. Some buying recommendation is always make sure to purchase from the original owner and one that comes from a smoke free home. Also it would help if the owner did the occasional cleaning maintenance as well.
What can you expect in terms of gaming performance? Well it will be able to play all games from medium to high performance. Of course this is based on namely the year it came out, and newer games will obviously need lower adjustments settings to get a smoother play.
If you are keeping tabs with the new Dota 2 game, you will meet the required settings to be able to play it. Don't expect to push the game graphics to the max as you will need a more expensive and up to date machine. But it will definately be playable.
The only game I found unbearable to play on this machine on any settings was the recent Witcher 2 game. Otherwise, you should be good to go. Hope this helps.
And if you could somehow save another $600 dollars in the future (adding your purchasing power to about $1200), then the best laptop for the money is Sager/Clevo.
Lastly, if you do decide to go with the Gateway 7811-fx route. Try sticking to that model as it includes the better higher resolution 1900 x 1200 screens. The later released model 7805-u came with a crapper screen to save on cost.