I've customized computer specificly for music and have used it with sonar and wavelab pretty much and the preformance is quite fantastic.

specs

-P4-3.02E with a P4P800 DELUXE mother bored.
-1GB PC-2700
-160GB HD 7200RPM
-16X DVD-RW/CD-RW Pioneer DVR-A09XL (the fastest DVD writer in the market)
-52X read and write CD-RW plus 16X dvd read Samsung Combo SM-352.
-DMX-6FIRE 24BIT/96KHZ sound card...here is a link comparing the creative sounds card Audigy platnum EX to the DMX. http://www.digit-life.com/articles2/terratecdmx6fire/

-430W POWER SUPPLY.
-Windows XP-PRO SP2. I will include the WINDOWES xp CD with it.
-I'm including 17" regular monitor and a wirless keyboard and mouse with it.

The asking price is $1500. If you have anymore questions...email me.