Don't be fooled by anyone who says building your own is hard. to have RAM and CPU installed is $70 a pop for just the RAM alone, unless sits offered for free when you buy it at the store. Installing those components literally takes 30 seconds and unless you don't know your own strength its downright impossible to break anything, and all the parts go together like legos. Plus with an OEM copy of your OS, clean install with no junk, parts go bad and they are a lot easier and cheaper to repair than a brand name (in some cases if a brand name component goes bad, you HAVE to replace it with the same one that went in, and they get expensive and aren't that great). With DIY you get the best bang for your buck, in terms of quality and performance.
specs to look at:
CPU: Dual core or quad core that is compatible with DDR3 (even dual cores are hard to push to the limit if you are doing audio tracks and a few VSTi's like SD2.0)
RAM: 4GB to 8GB DDR3 aim for at least 1600MHz
MOBO: ASUS and Gigabyte are great brands, look at their $100-200 boards
HDD: Western Digital's OEM packaged Caviar Black 1TB drives are $100, best and cheapest in the market (one HDD that is not in a RAID configuration is still too fast to bog down)
GPU: Anything NVIDIA or ATI that is cheap that works if you are not gaming it really doesn't matter how fast it is.
PSU: At least 500 watts for the above setup 600-750 is best, I would recommend Corsair and Antec above all others, they are reliable and have excellent efficiency. If you have big bucks, enermax 1000watt will last your for life.
DC Drive: you just need one that can read and burn DVD's, nothing fancy
As the debate for Intel vs. AMD, its up to this, your budget and the bang for the buck. AMD will give you better specs for the price and a slightly lower performance compared to the much more expensive Intel equivalent (the Intel wins by marginal results and are 50-100% more if not greater in price)
a whole build will take you on average about three hours from opening the package to first turning on the computer and about another two hours for the OS and software, expect it to be about 5 hours to go from in the boxes to recording music, its quick and actually more fun that it seems.