Andrew, welcome.
You have TWO SVS subwoofers AND powered towers?!?! Good grief. Time to diversify your assets!
I still own a Polk RM3000 sub/sat system (about 15 years old). It was a fairly high-end setup when I got it, and still sounds great in the bedroom. It has a "voice" that I like very much.
But the Axioms are *transparent*. More importantly for me (and for you too, I believe), the addition of a true three way speaker really opened my eyes as to how glorious Stereo can be. While your Polks are a very fine piece of engineering, I have never heard any powered towers that sound as silky, wide and full as a comparably priced three way speaker. Powered tower speakers seem to me to be just a two-way system mounted atop the same box as a subwoofer. Consequently, you lose the placement flexibility you need for both bass and imaging.
With the SVS's (!!), the Polk subs are totally redundant. My opinion is that you would be absolutely delighted by the soundstage presented by the M80's. I have M60's, and am astounded by the size and depth of the sonic image.
And, oh baby, get the QS8 surrounds. They'll change your life.
