Subwoofers.... one 10" or two 8"?

I'm looking to fill out the bottom of my simple 2 channel system  (Musical Fidelity X-Ray CDP through Peachtree Audio Grand Integrated amp to a pair of Mirage OMD-15 full range speakers).  I occasionally will play the TV audio through the system for movies, but not interested in an HT setup. Music is the prime focus. The room is "medium" size.  I know that will not give the deep bass feel of a 12", but the difference should not be too great, and a 12" may be overkill for that room.  I've also considered getting two 8" subs to keep the sound balanced between the left and right channels. I think the  8" may be enough bottom for my room and tastes. I'm on a budget so getting a pair of anything bigger than 8" may not be in the cards.

Any opinions or suggestions as to whether I'd be better off with one 10" or two 8" subs?