I totally agree with Chess. I had exactly the same experience with my M3s when they first arrived. I was so disappointed that my Panasonic seemed to sound better and began wondering if I'd wasted all my money. Like Chess said, I gave it some time and things still didn't improve. I finally discovered that in my haste to hook the speakers up, I'd used some old, cheap worn out oxidized thin wire. I immediately bought some oxygen free 12 gauge wire and tried it again. Viola! I was much happier now with the sound.
It took me a little time to understand that I wasn't suffering from ear fatigue anymore and we actually play for 8 hours at a stretch these days. The neutral and smooth sound of the Axioms sinks in slowly and you realize it over time.
I'm sure you'll enjoy your M40s very soon.
