Spiff - The EP-600 does everything the 500 does, plus it hits about 1/4th octave lower and about 2-4 dB higher SPL, depending on frequency. The EP-500 is just a more palatable package for most homes.

Having had "Epic" series subwoofers in our system for over 6 months now, nothing has changed my mind about their performance. They are flat-out spectacular.