Alienware isn't too bad. Personally I like Falcon Northwest and Voodoo PC more. Those are definately respectable companies. If you bought a Voodoo Omen PC, you would have so much more respect. It may be expensive, but it's SOOO much more worth it than an Alienware.
Velocity Micro, Vigor Gaming, Hypersonic and Gateway and some other smaller companies aren't too bad, they actually have some nice setups too. Yes, I did say Gateway. They used to be part of the trinity of shit, but they're actually quite respectable now and their new FX gaming line has gotten some good reviews for giving good performance at a decent price.
Apparently Commodore is back from the 8-bit grave, but instead of consoles, they're building high-end PCs now. From what I heard, they're supposed to be pretty expensive too.