I am a new owner of the M60's and Velodyne DLS-4000($ 399 on sale now, maybe cheaper on the net). I am far from an audio expert, but I have no complaints, just the opposite. The Velodyne is cheaper than the Axiom subs, though not as pretty, maybe not the equivalent sound wise, have not heard the Axiom subs. Seems to match the M60s, VP150, and QS8s very nicely though. I use the LFE from my Yamaha 2400 and I set up using YPAO, so maybe the receiver is doing a lot of work for me.
I would say spend just $ 200 more and get what you want. Divide $ 200.00 by the number of years you plan to have the speakers. Report the "per year" number to your wife. Let me know if you are ever near Morristown, NJ you can have a listen.
