I looked into gaming laptops somewhat as well, from what I remember most of those specs you would like will far exceed your budget. The highest graphics card you can get inside of an XPS 15 is the 540M, XPS 17 bumps up to 555M, and with the alienware MX14 you can get a 2GB 650M. The MX14 looks like the only available Dell option inside of your price range that offers sufficient specs. I decided against purchasing a Dell product, mainly because you can no longer remove any options, often times it comes packaged with useless stuff you must have (40 dollar digital camera, would rather just have to 40 bucks back but no longer possible!). I also did not investigate HP, have had many problems with them (I spent an extra 30 bucks on my desktop configuration for a wireless card which would not ever work, finally one day I tried moving my wireless router literally next to my case and then I actually got a signal, kind of defeated the purpose, and that machine was dead after about 3 years of light use). Most other major manufacturers do not offer much in the way of gaming laptops from my experience (at least not in that price range), I seriously investigated a gaming laptop before deciding on building my own desktop, and I could not be happier with my decision.
*Edit* I forgot to mention that HP generally does have more options than Dell and you can get much higher specced components for pretty reasonable prices, they also seem to offer lots of free upgrades, however this approach makes me wonder what the quality/construction of the components are, especially considering my past HP experiences. *Edit*
I believe they were sold out for awhile, not sure what their status is now. I'm sure a lot of it went into marketing, research and development though being their first computer. I also saw a prototype for a gaming pad, had two controllers on each side of it, I believe they are developing it now.
Yeah I kinda agree. Laptops are good maybe for kids or light gaming, really wouldn't consider buying a gaming laptop over a desktop because you're missing out on a lot. They're not really upgradable and you can't really overclock.