I've made some additions and changes as suggested by you guys.

I'll be going through the list and checking for inconsistencies (price, links, availability) hopefully in the near future. Audio-gd and Pacific Valve stuff hasn't been updated yet. I couldn't find official documentation for the Linn or Naim DACs, so I'll wait on those until they're on the manufacturers' websites. Just let me know!
I decided not to include any Behringer units because their DAC functionality is ancillary to their main functions as EQs, feedback destroyers, etc. I also chose not to include modified units that were not modified by the original manufacturer, because most of the time those go against the original warranty, and because mods aren't exactly 'original work.' I could see those getting out of hand with regards to keeping the list tidy. Thanks for the heads-up, though.