I'd say Falcon Northwest, both for performance and support. In fact, order by phone and offer to write something good about them on the web. It doesn't hurt your chances of receiving a well thought out build.
Alienware has slipped on performance and seems to have traded perfomance for flashy glitzy appearance instead. Pricey.
ABS has stayed about the same, they really haven't been leaders of the pack, but they're one of the better companies for support.
Voodoo - To pricey for performance. I prefer to pay less and fix, repair, optimize myself.
Cyberpower - Decent if your a tech junky and don't mind repairing, taking care of little details, and optimizing yourself. The systems are normally lower priced, but they rarely handle the small details that makes a leader. I ordered a system from them a couple of years back. When it arrived the cables were a mess, the vid card was loose in the case, the memory wasn't seated correctly, upon scanning the registry I had a huge number of errors that should have been taken care of before shipping, there was a software conflict with burning software, and (of course) the system wasn't optimized and defragmented. The system wasn't a problem for me to fix.
Vicious PC - nice, but relatively new and unknown. Wouldn't count much on support.
Dell - Great if your a office junky and not a gamer. Beware the infamous Dell power supply, and the PITA case.
Systemax - Tiger Direct, enough said.. Wouldn't wish them on my enemy.