Thanks everyone for suggestions and comments.
I've made my decision, now, and the new digital front end is in place and sounding nice.
So...it's out with the old...

and in with the new...

That's an ASUS EEE 901 PC laptop (with a miniature 8.9" screen), employing solid state drives. It's pulling FLAC files from a drive attached to the PC in the basement, playing them through ASIO4ALL-equipped FOOBAR 2000, and passing the files into my brand new Audio Sector USB DAC (by Peter Daniels).
The laptop is dead quiet. The DAC is a solid piece that, despite its stripped down aesthetic, reeks of high construction quality. I'm pretty excited by the setup right now.
It sounds nice even this early in the piece. I'll probably gather the enthusiasm to compare it to the modified SB2 I've been using in the reasonably near future.
Almost everything is working very smoothly. The only little problem is that occasionally I'm getting tiny pauses in the music. I suspect this is due to the fact that my new audio PC is receiving files wirelessly from the PC downstairs, and there are tiny interruptions in the wireless signal. I have the capacity to hook up an ethernet connection, and will probably do so in the next few days. I hope that fixes the issue.
Chad