Building your own computer can be daunting, especially if you have never done it. Don't let anyone tell you it is a simple task. It isn't.
But, buying an OEM computer today is not the best choice either. OEM's have become so cost conscience they are stuffing the cheapest components they can get into the systems.
Generally speaking, you will spend more to build your computer than what an OEM system will cost, IF you chose to use high quality components.
For me, there is no other reason to build a computer, other than I demand the best components I can get. That does not equate to the fastest system, but it does translate to a very reliable system that will just simply work.
Someone mentioned pricewath as a good site to get prices and find companies that sell computer products, but you need to be cautious. Some of those low-ball prices are made up by the shipping charges and some of those companies are fly-by-night companies that do not ship anything but will merrily charge your credit card and make excuses for not shipping for 30 days, which happens to be the time period for filing charge-back requests to most credit card companies.
Here are some reputable sites I use.
http://www.comp-u-plus.com/ Good prices, fair shipping costs.
http://www.microx-press.com/ Not the best prices, but they have a lot of the software at good prices.
http://www.antec-inc.com/ Get the HD Cooler and fans for your system here.
http://www.techstore.com/ Good place for the case. They carry a good line of Antec cases, which is what I would recommend.
http://www.crucial.com/ Memory. Cannot go wrong with Crucial ram.
Hope that helps.
------------------
Roy "Skuzzy" Neese
President, AppLink Corp.
http://www.applink.netskuzzy@applink.net