A/V 2.0 / 2.1 DAC recommendations?

I recently picked up a pair of Mackie studio monitors on the cheap, and I'm getting tired of listening to onboard sound through them. My board has SPDIF out (RCA jack, not optical), firewire, and obviously USB, so I'm flexible as far as connections go.

What would you guys recommend for a good 2.0 or 2.1 DAC? I may be grabbing a subwoofer with my income tax returns (I already have one in mind - the Meyer Sound MM-10), so being able to output a bass-only mix to that as well would be nice.