If it is worth it is really up to you and your taste. When I went for an audition at the Axiom plan I went with a friend and we compared the M60s to the M80s. Although they sound very similar, there is some differences. We both agreed that the M80s had a bit more detail/forwardness in the midrange area and a heavier bass. While I preferred that, my friend preferred the overall sound of the M60s.

Bruno
M80s/VP180/QS8s/EP600/AVR-890
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"The problem is choice..."