The power amplifier in my EP500 v2 failed a couple of months ago, so rather than replacing the amplifier, the nice folks at Axiom let me trade up to an EP500 v4. If you're like me and primarily listen to music, you will be enthralled by the EP500 v4, the bass response is deep, tight and well articulated. It's the most satisfying subwoofer for music that I've listened to. For home theatre, however, it initially sounded a bit anemic to my ears compared to my old ported EP500, that guy could really shake the woodwork. The nice thing is no trace of the chuffiness that I sometimes heard from my old EP500 when playing movie LFE.