With my Bose 701's I have 2 x 8 inch subwoofers in each tower, which gives me pretty good base for movies. The base is so good that I wonder just how much more a sub would offer to me. How would the M60 or M80 compare base wise?

Receiver: Yamaha RX-V2200
Main: Axiom m80
CC: Axiom VP150
Surround: Axiom QS8
Sub: SVS PC13-Ultra