I'm running a Macbook through a Locus Design usb cord into a PS Audio Perfect Wave DAC. For the moment I'm using a Lacie Hard drive, which is reasonably attractive and quiet. Software is iTunes, ripping is AIFF, error correction is on. I'm quite pleased with the PWDAC, and the setup easily bests the modded Musical Fidelity A5 CDP it replaced. The Perfect Wave may be worth a look for you.
I don't feel as though I'm getting everything out of my setup; I detect a bit more lifelike timbre when I use a Jolida CDP as the transport. I'd be interested in your thoughts as you progress; I think you'll be very pleased with the combination of convenience and sound with a computer front end.
John