Also, the EP500 is a sealed unit, where the EP175 is a ported. Not that any of the Axiom subs huff, but I found that the sealed units give a much more integrated sound with my speakers than I have ever achieved from a ported sub.

Anthem: AVM60, Fosi DAC-Q5
Axiom: ADA1500, LFR1100 Actiive, QS8, EP500, M3, M3comp, M5