Yeah, I second the recommendation to get your own custom machine built at a local computer store (assuming the store has a long and well-deserved good reputation).
Decide what you want your machine to do, research the main component alternatives, get the computer shop's recommendations, and go for it!
Don't forget to check the latest offerings in keyboards, mice, joysticks, and other goodies. Be sure the computer has enough power and cooling for everything you want to do.
You might wind up getting the core computer at the small local expert computer shop and some of the accessories at larger chains like CompUSA. Just be sure you talk with the best experts available and get good guarantees.