The tuner module is not a completely independent unit. From what I understand, it doesn't just receive serial commands. Some of the work is done by the DSP on the empeg itself. So you can't just connect it up to a PC without an empeg in there somewhere.

You can perfectly well control the tuner from a PC as long as you're installing both the Empeg and the tuner as a matched pair. Then there are serial commands you can send to the empeg (although now that I think about it, I'm not sure how many of those serial commands can apply to the tuner).