If you like the Magnepans (I am a Maggie owner) trading them in to get some 'other' sound is not going to make you happy if yu like the maggies except for wanting some extra thumpability to rock out at times.
For 4 grand your could buy a Fathom. or a pair of REL.
those are the brands subs I would recommend to add to a 3.6
For 4 grand your could buy a Fathom. or a pair of REL.
those are the brands subs I would recommend to add to a 3.6