Waker, while either a 14B or a couple of 7B's would work well with your Maggies, I can tell you from experience that a pair of the 7B SST amps will work great with Magnepan MG 3.6 speakers. Like they were "made for each other". (The SST2 will presumably be even better.) I have another one powering my Maggie center as well. Rumor has it that the owner of Magnepan uses the 7B/Maggie 3.6 combo in one of his own installations.
I liked the opportunity to place each amp right next to the speaker it is driving, which is where they are now. Running balanced interconnects from the SP2 pre/pro to the 7B SST amps, I wasn't worried about longer distances on those runs. (It really shouldn't be a problem with long -- I'm talking maybe 12 to 15 feet here, not 50 -- unbalanced interconnects either, as long as you don't have a power cord running in parallel to the interconnects.)
Even though you already have cables that you cannot replace at the moment, so placement of the amp near the speaker isn't an overriding concern right now, it might still make sense to go with the 7Bs just to be able to lug them around individually without requiring a fork lift or a followup visit to an orthopedist. :>)
Enjoy!
Burke