The only computer that ever came to me whole was a Gateway 2000 486 DX/2 50 Mhz. Since then I have been building my own together piece by piece (which I call 'Frankensteining'). I can put a computer together for a highly reduced cost, but at the loss of any technical support should something go wrong. However, I've managed so far just by dealing with the manufacturers of the individual parts. I wouldn't recommend this to everyone, but if you are a computer enthusiast, I would highly recomment putting your own computer together if you haven't tried it already.
I recently upgraded my computer part by part. It was a bit aggrevating at times, but well worth the $250 I saved versus retail. It is a PII 350 Mhz, 128 MB SDRAM machine. You can get all the specs on it by clicking here.
I recently was given a P166 which I'm throwing some scrap parts into to make a Linux server for my home network.
I also scored a great deal on a PII 300 Mhz, 64 MB SDRAM machine. Found a guy looking to sell it cheap, and picked it up for $300. Great machine, good deal.