Compaq is the work of the devil. I came to this conclusion through my own experience, and far too many people I talk to agree. I do have one Compaq server running Red Hat now, however, and it works fine.
Dell's, IMO, are far better. They're customer support is awful, but the computers are pretty darned good. Yup, I have Dell servers too. You can even buy Dells with Red Hat installed. Crazy.
I'm sold on IBMs, now. Every IBM i've bought, worked on, and/or used has been amazing. Just perfect. My IBM linux servers are my favorite. I have all three manufacturers' servers in a production environment, and I say to go with IBM.
-Andre