matty, first of all, i would get the upgrade done to the tsm mxe. they will sound very much fuller, more robust, focused and expansive. listen to them for a few weeks and then you make the decision whether you want a sub, first hand or not. the cost is minimal but call the factory for a quote. just a few day turn around too. read "merlin upgrade experience" and "have you heard the new merlin vsm mxe" on agon in the archives.
call me at the factory 585 367 2390.
then i will go through the sug thing with you too.
best regards,
bobby at merlin