Lian-Li (as far as Lian-Li go they make the highest quality custom cases).
Main reason I make my own is cause I find it relaxing and somewhat fun to do, I have a different attachement to a rig I make myself. I have been asked to make 2 PC's in the near future, one of them will be a high end machine so I will get to make the above (only if it were for me =[ ). Premade machines have limititations and/or make it extremely difficult to make customize with the companies warranty/policies issues and most of the time customer service there lacks.
But if you are looking to buy a premade machine than look no further than the Reactor, only fans inside are for radiator, liquid spills out and covers all hardware soaking them all in mineral oil.
This would be the cost if I build a Reactor to my specs, pure gaming power.