I have a M&K MX-350 sub (and plan to keep it) with the S-150THX system. Thinking about adding a SVS Sub. Not sure whether to pick the 16-46, 16-46+, or the CS_Ultra. I'm happy with the MX-350 but am looking for additional very low frequency content. Room size is 4500 cubic ft. Cost is not really an issue, but I'm not really excited about another amp to put somewhere. Any thoughts???