Ask Slashdot: Buy Or Build a High End Gaming PC?

An anonymous reader writes: Looking at some Black Friday ads, I'm seeing some good deals on Alienware and other gaming rigs that would be cheaper than building them from scratch. If you built or were to build a high end gaming rig, what would you suggest? Or would you just get a prebuilt system and customize it to your needs? I'm not looking for cheap, I want best quality and performance, but not overkill that would rival supercomputers and at the same time break my bank account. It would be a Windows system to keep my family happy, but possibly dual boot with Linux to keep me happy. It will be located in the livingroom hooked up to a regular monitor and the big screen TV, replacing a budget PC that's in there now.