Jim,
Congrats on your purchase. I envy your ability to pick up the stuff directly from Axiom. Also, you're to be especially commended for purchasing the M50s. They are seriously under-represented on this forum.
With that all being said, you don't need to worry about the EP500 being too much for your living room. It has its own volume control so you'll be able to dial in its performance easily enough. When properly set up, the sub should only call attention to itself when its supposed to. It will seamlessly fill in the bottom end and make it seem like the sound is coming from the M50s. As good as you think the bass is now, you'll know you made the right choice after hearing the complete system.
