Depends on what power you're running to them. I had a Stetsom 2k6d running to the MX 15" and it was pushing it to it's limit. So if you're running more than about 2500wrms to each sub the XXX is the better woofer to have gone with. I liked that the MX had the Neo mag so it wasn't all that heavy and I'm not positive but I think I read somewhere that the MX had slightly better SQ (although I think there was some mechanical noise associated with it as well). Either way if I were you I would have bought some TC 5200/5400's, Xcons, or even the new Nightshades for around the same price.
