What is the crossover set at for the M80s? You should be able to get a decent kick drum out of the M80s as the best punch is in the 50-80hz range. I have my M80s set to 40hz and with the right amount of power they have some great punch to them. The larger the room the more power required to get this punch, so a separate amp might be required. A good sub will also help in this area but the majority of it I feel comes from the mains.
If you still want a musical sub, any of the subs mentioned on this forum will work as they are all qulaity subs. Some do say a sealed sub is better as it doesn't reach as low (usually) as a ported sub. I had a SVS PB12-nsd that lots of mid bass punch to it. The PB12 has a bump in the frequency response right around 50-60hz, really good punch out of this sub but I felt it was unnatural and was a little annoying, too much like a car subwoofer.
