Funny, I have the Outlaw sub and about the same size room as you do. I love my M60's and do not need much more from them. With the savings that you get from going with the M60's I would go with dual Outlaw subs. I will be going that route once my wife turns her back on me. You will be very happy with the M60's but if you are still wondering you may want to check the Axiom listings to see if an M80 and an M60 owner is in your area.
I have heard that the M80's are a little more of a difficult to place and they are a power hungry set. If you do go the M80 route you may want an amp.
