If you don't want to make one yourself, but still want the best quality system you can get, try:
http://falcon-nw.com/
They certainly aren't the cheapest, but you won't find a company that sells better quality systems. Alienware used to be like this when they first started but then they went for quantity over quality.
Check out the paint job on this sucker:
http://falcon-nw.com/images/exotix/F...-off-large.jpg