I went from Polks to Axioms myself, and my immediate reaction was that they sounded thin, too. I loved the detail, but I thought something was perhaps missing, and this was with M80s. Still, I listened to them more, and when I finally heard the Polks again, they did sound bloated and muddy compared to the Axioms. I haven't looked back since. I wouldn't say the sound is perfect, as I do think the highs could be a bit smoother (which is why I'm curious about the v3 M80s), but augmenting my system with more amplification and great subs has balanced the sound quite a bit. It certainly knocks the pants off the local theaters, and I don't know anyone with a better system for music. Not all recordings sound great on my system, but the great-sounding recordings sound really great.

I realize I've invested quite a lot into my setup, so it's not a direct comparison to your own experience, but I think our Axiom vs. Polk impressions sound similar.