Hello rambilt, welcome. They are probably going to drum me out of the forum for this, but I have to wonder whether changing to the Axiom line is *necessarily* going to be an upgrade for you.
I've owned Polk speakers and like them quite a bit. I have an older sub/sat system like
this one; I bought Axioms because I had an itch for "different", and wanted floorstanding speakers. I am VERY happy with the M60's.
But my take on the
RT55i, based on Polk marketing and my personal experience with a very dissimilar model, suggests that it is a very capable speaker. Unlike my situation, you're NOT going to be spending a lot more money on your new speakers than you did on your existing ones.
I don't see you mention a sub. If you are trying to get reference-level volume from bookshelf speakers without a sub, you will likely always be disappointed; it is a physics problem. Likewise, while the Axiom tower speakers would probably give you a much "bigger" sonic image in every respect than the Polks, even a big-box speaker is not going to thump you in the chest like a dedicated subwoofer and those extra few hundred watts.
So, more info please!
But to answer your question directly, I have M60's in a 13x28 room with cathedral ceilings that adjoins a 12x14x18 foyer. I drive them with a very modest Denon 1804. I do not lust for either the M80 or for more watts. I think the M60 would be fine in your room, and you might very much like the *sound* of the Axioms better than the Polks. The M60 and M80 have similar sonic signatures.
But I really think that a sub is your answer if you don't already have one.
