Hello!
I am new to Volumio, and am very impressed with it so far!
I took a Raspberry Pi and a Mackie Onyx Blackjack USB recording interface (DAC/ADC), both of which I had sitting in my office, and prepared an SD card with Volumio on it, and it just worked. And it sounds fantastic!
Info on the Makie Blackjack - http://www.mackie.com/products/onyxblackjack/
The Mackie Blackjack isn’t something you might pick as a DAC - but I was pleased that it just worked! The DAC inside is a Cirrus Logic CS4272.
I also have a Raspberry Pi B with a Wolfson DAC. I would go to the effort of making that work, but given that I don’t have a spare Wolfson card, I would rather not invest time towards that end.
I am very interested in getting an I2S DAC for a Raspberry Pi B+. Most likely the IQaudIO DAC+, but they are currently out. If it works out, I want to place 3 around the house.
I would rather build something around the UDOO, given that it is faster than the Raspberry Pi and still at a fairly attractive price point. But there seems to be overwhelmingly greater support for the Raspberry Pi from DAC manufacturers as well as on the forum.
Apologies for the long post, and for rambling a bit. I wanted to share that the Mackie Blackjack just worked! 
