Darth, we've discussed the VP150 over at the Axiom forum (apologies, again for it getting testy), but we didn't really touch upon the EP500. The drawback with the 500 is that it's so new, not a lot is known about it yet. There are a couple of members at the Axiom forum who have it, and are happy with it, but we haven't really heard a lot about it yet. However, I don't know if you are aware of this, but it won the 2004 Audioholics Product of the Year Award for best subwoofer.
http://www.audioholics.com/productreviews/avhardware/2004productawards.html
That would seem, to me, to be a pretty good endorsement, and would put my mind at ease about it.