Just an update.. I got the speakers yesterday morning, and have been playing them almost nonstop. The tube amp proved to not have close to enough power -- it sounded sweet, but just couldn't do the job. I connected the old receiver from my college days, and it performed shockingly well! This thing is.. don't laugh.. a TEAC AG-680 that I bought in 2000 for a couple hundred bucks. It was always pretty decent, but I am still in disbelief at how well it drives the M80s. It's actually good enough that I can put off buying / building another amp for a little while.
Even though I have heard them before (and connected to better equipment than I have)... WOW!! Every single thing about my stereo is night-and-day better than before. Even the subwoofer (a Polk PSW505) sounds dramatically better, because the Axioms can get low enough to meet it at a frequency where it belongs.
My impression of the M80s is crystal clarity and effortless dynamic range. I know that sounds like the kind of generic line you would see in quotes on some speaker company's website, but it's how the sound comes across to me. I can hear everything in the music as if it were playing by itself, even when the whole audio spectrum is filled with much louder signals. Drum solos are amazing. I've seen a lot of people describe them as "bright", which would seem to imply that they favor the high end, but I really didn't get that impression at all -- if I had to use one word to describe the sound, it would be "clean".
On the downside, defects and distortion in recordings are agonizingly obvious. The M80s are NOT forgiving of poor quality recordings. At all. Some music just doesn't sound that great when you can hear all the details. Some records have intermodulation / harmonics and even clipping in them (that I never noticed before). That sounds downright horrible. More forgivable are old recordings -- mostly stuff from the 60s for me -- that are full of tape noise and missing part of the low and high end. These don't sound "bad", but it doesn't help to play a bunch of near-perfect sounding tracks before listening to them...
