If you can build it yourself it will be way more powerful and will fit your budget. If you really have no experience in that field use a website called cyberpower they build computers and let you know if all the parts are compatible. Alienware is a complete rip off. Not only are their computers overpriced they are not even good. Ask anyone on the forums and they will agree.
You can start here and build your own make a list of the parts then order them your self. At the first two sites they allow you to build the rigs with the configuraters. Just play around with it and learn at the same time.
The last two sites are tigerdirect where you can but barebone kits and put it to gether yourself plus they sale gaming rig already put to gether. I hope this helps and good luck to you.