I have thought about the ep600, wish I knew more, or could read a true review of it. One problem that I have, and others may have with the Axiom 600 beast sub, is I can buy 2 of the HSU, and their seperate amp for less (also free shipping) than the (1) 600. Not that 2 makes em better, but I think they are 2 proven subs, and SVS 2 subs, either the 16-46s or the 16-39s 525 watt powered, would cost about the same as 1 Axiom, 2 ultras would only be a bit more $$$. I talked with SVS, and sent their staff a plan of the room, waiting back on their reply. Did not know if HSU had the ability to do that.
