I buy from a lot of places, actually... NewEgg, CDW, Crucial (who has some of the best customer service there is, even on par with Speakeasy), etc.
NewEgg:
I can't recommend NewEgg highly enough. They're a very basic, no-frills kind of company. They tell you exactly what you're getting up front, they ship it on time (often for free), and they have excellent customer service and competetive prices to boot.
CDW:
CDW specializes in business systems, so they aren't very competetive on the high-end performance market, but for storage, keyboards, mice, speakers, and the like, they're excellent. CDW is very professional - even moreso than NewEgg. Unfortunately their prices tend to be hit-or-miss, but they're definitely worth checking out.
Now, really, between those two sites, you could buy everything you could need for a computer and get good prices. But if you want to do more bargain hunting, I'll make a couple suggestions:
1. Use the
Better Business Bureau religiously. As a rule of thumb, if a company isn't in good standing with the BBB, they don't get my money. If a company is in good standing with the BBB, they may still be questionable, but at least you've got some leverage if they try to rip you off -- believe me, most member companies don't want to get on the BBB's shit list.
2. If you still have reservations, check Tom's Hardware, Ars Technica, OCP, and the like's forums to see what people think. Those guys
really know their stuff.
3. You can't get a video card there, but Crucial is AWESOME for RAM. Personally, I don't use them because I favor Corsair RAM, but Crucial offers some of the best customer service in the world -- the quality of their product is up in the air; I don't like it because it doesn't overclock well, and I hear people having problems with it rather often, but I also know a lot of people who absolutely swear by it, even for mission-critical applications. Plus, Crucial sells a
lot of RAM, so it stands to reason they'll have more people reporting problems than other manufacturers -- more people have it. I actually use Crucial memory in one of my machines, and I've used it for years in my main machine (I've just recently switched to Corsair) without any problems.