Is this more of a question of which manf. to pick or which CPU?
I've built several of my own machines and also for family, and I prefer to do things that way, you get exactly what you want. Having said that, the main box I use now is a Dell I bought last year, and although it's not ideally suited for upgrades or tinkering, it's served me well and the few problems I did have were taken care of with BIOS updates. This machine is a 1.4gHz P4 with PC800 RDRAM; I've always been partial to Intel procs myself, but I've heard good things about the new AMDs. If I had it to do over again (buy a PC vs. build one) I think I'd shell out a little more and get one from
Alienware, for performance reasons and just because they seem to have an excellent user rating. Plus the fact that they do things as you would, build the machines from scratch and don't skimp on components. There are alot of other 'custom' shops popping up now, but I'd still go with them, more established and have good customer support (or so I'm told). They also have a mix of AMD and Intel boxes to choose from.