You'll likely miss the EP500 if you watch movies and home theater. For music in two channels, not so much unless, like me, you enjoy Wurlitzer theater pipe organ recordings, and the 500 really does increase the low-frequency impact.
The M80s have excellent usable room output down to the mid-20-Hz region and do a fine job with most low-frequency musical instrumental output. Only some pipe organs have energy below 20 Hz, and the fundamentals are at a very low level. The 2nd harmonic at 32 Hz carries most of the audible energy from a 64-ft pipe. Still, the EP500 does add some musical impact.
As to using your Macs and Carvers, if they're working fine, why change? At Axiom, we're firmly on the side of no audible differences in amplifiers except maximum clean power at high playback levels.