IMO dont go PC build a Hackint0sh something like this
http://lifehacker.com/software/hack-...800-321913.php
Then what you want to do is download a pirated (or buy) Logic Studio. The pirated version is about 50 gigs. With Logic you should be good to go!.
The PC is roughly going to cost you under 1000 and with the rest of your cash you can spend on a nice Midi keyboard such as an Axiom and get KRK monitors then your set