If you are building this as a car audio DAC, then it should have four outputs (front left, front right, rear left, rear right) and a sub output. I think Doug would have some input here as to what features would be desirable in a high end car audio DAC. I would suspect multiple digital inputs, say, from a CD player for competition use. Perhaps a "tape monitor" style looped digital-in-out-in that allows for third party EQ's, DSPs, and so on.

Calvin