Mike, I had the EP600v2. The sub suffered from too much distortion likely due to the port but not completely I think. Two EP600s would have been worse. It was as bad an experience as driving on Portage Ave with the year-round construction...LOL! It had no problem pressuring my 4,200 cu.ft. space but it wasn't a linear experience. The 800v4 was a God-send. It cleaned everything up and I have tight, transparent, effortless, fast, distortionless bass throughout my room and it doesn't distort no matter how much you turn it up. It's quite amazing, really.
You only need one 500v4. SlimPikins has one in his 10,000 cu.ft. space (for music only) and loves it. I tried a 500v2 in my 4,200 cu.ft. room a decade back and it had no problem with music and movies. If you do get one of the DSP-based Axiom subs, you might want to consider asking Ian to give you the gut punch mode (read my review).
The VP160 is sooooo much better than the 150. It's a no-brainer. I just upgraded from the 150v2 which I think you have, to the 160v4. So glad I did.
