Look around: you might have a capable shop in your own neighborhood. My computer was built by a shop in Austin (the first time) and rebuilt the second time by a local shop here whose owner is into, guess what, computer recording. It runs like a train. Now a guy I know from church has opened a shop and I have had him replace (so far) a hard drive and a power supply, on two different computers. He is definitely into robust components, and he has the capability of testing that I don't have. The net result is that I don't spend much more than what the parts would cost, and both my computers are running better than ever.
He's also available to answer questions, which is a little different from something you buy off the internet.
Concerning which: my wife bought a 98SE computer via internet, and it was fine until the hard drive failed. I decided to upgrade to XP, and was stuck with buying the full version, because the computer came with ZERO discs! Buyer beware.