Why not get a DAC that has a headphone amp built in and also has the pre-amp output you need? That way, you can get you some good headphones next to use with the killer DAC you have. The Peachtree Idac has no headphone jack. I've also always thought Peachtree was a little overpriced.
Look into these. Each also allows you to hook up both via USB and/or optical:
Maverick Audio D1 Plus (tube amp sound for your speakers)
Audio-GD NFB-11.32 (I would expect the DAC to be a bit better than the Maverick, but it is more expensive)
Emotiva XDA-2 (probably same class as NFB-11.32, but not certain)