Hi Derek,
we are doining a project with mini itx boards here. I have had very bad experience with different VIA chipset boards (computer noise in the audio path) so we went for the Intel D201GLY or D201GLY2 (fanless - needs extra cooling) with a Midiman Audiophile 24/96. It needs a BIOS update to run with the Midiman card, however. CPU is 1,4 GHz Celeron. Very clean audio running on a buffer of 64 or 128 samples.
The board has a SIS chipset which really surprised me to work but it actually did! It also has a better a better performance that VIA boards at the same CPU speed. On top of it it is the cheapest mini itx board at all.
Ingo