Ask HN: Where to buy a desktop PC?
Any suggestions for online retailers to buy high quality desktop pcs from?
Having said that, I've always found Dell desktops to be really good. A bit less extra crap pre-installed than some other manufacturers (I'm looking at you, HP), and you have a 50% chance at good support (I've called in 4 times over the years - 2 were teh sux0r, 2 were great help). So if you gotta buy online, Dell is my recommendation.
If you build your own, try and find a local shop (here we have bCom and Memory Express) - they will almost always be cheaper than Future Shop and Best Buy.
If you do feel you need a desktop (if you want dual SLI graphic cards or TBs of hard disks in raid 1), I have to agree with the concensus and build your own. It is fun to learn, easy to do, and cheaper.