For a sub... Would this work?
Buy like 4-8 of the mono price in wall 10" subwoofer
http://www.monoprice.com/products/pr...seq=1&format=2
And build them into the riser for a second row of seating in the "theatre"
Edit.. Should add I have experience doing car stereos and live sound reinforcement.. I have seriously considered putting a DJ system in my theatre... But I have pretty decent knowledge of ohms, and watts etc. just no idea of what's good bang for the buck home theatre stuff.