I know you don't want to build your own, but if you want a gaming machine you'll save tons building it yourself.
http://www.newegg.com is an excellent site for parts.
But if I needed a PC and didn't want to build it, I'd go with Dell. Check their outlet center and look for one of their XPS boxes. I think you get a 90 day warranty with an outlet PC, but have the option to upgrade it. The best time to check is during the very early hours of the morning. People grab the outlet deals as soon as they show up during normal hours.