I was thinking more along the lines of this but even taking something like this and toning it down by using a single, modest video card (the one you have now is decent enough; better than mine, actually) rather than the dual HD 6790 setup and omitting the SSD would net you a far better rig for cheap. That rig is $759 if you drop the SSD and video cards, and you can save another $100 if you have your own OS.
Thus far, we really haven’t made a decent gaming laptop. Those that are technically laptops and have more than half the gaming prowess my rig does tend to be tied to a wall outlet, thus defeating the purpose of a laptop.
BTW, I found four refurb XPS 600s for $300 on eBay
@HungryGuy I’m not so sure about the RAM. There is a point of diminishing returns; I have yet to need all 6GB I have. Granted, I use more than 3GB when I run hefty apps/games, but I think 12GB would be an unnecessary expense. I would say 6 or 8GB RAM (depending on what sort of RAM setup you have) would do the trick.
And don’t skimp on the power supply. You may not need a big one (600W should suffice for a single-GPU system), but you do need one that is stable, reliable, and puts out clean power. Pay the extra few bucks for a quality, brand-name PSU ;)