I built my own rig, mainly because pre-builts suck weinershnizle (What does that even mean, it just sounds funny, I mean come on.... WEINER!!) Anyways, here are the specs:
AMD Phenom II x4 @3.2 - 3.8ghz (Depends on the day)
4 Gigabytes of DDR3 1066 RAM
ATi Radeon 5770 (OC'd to 1000 core and 1300 memory)
I also have a 22' 1080p LCD

Please note that I run all aftermarket cooling, on the Graphics card, CPU, RAM, Northbridge and Southbridge. If I can get paid a decent wage this summer I'm going to go with Liquid cooling, it saves me a lot of pain (Did it on a different computer, soooo much easier than air.)