Knik's right, you can easily get a really swish gaming rig for £500 if you build it yourself or get a friend/family member to do it if you're not technically minded, and I'd never buy a pre-build anyway. Same machine that would cost £800-900 in Currys would be that much cheaper if you source the parts individually and put it together yourself. Not only that, but it's much more satisfying and you get to understand the particular nuances and personality of the machine intimately as you tune it up. I was genuinely gutted when my last rig finally died on me.

Pretty sure the other PC builders around here would agree with me, there's a few of us on the site.