Advice on replacing 12 in woofer in Martin Logan Monolith III's

Just thinking,  if you are using electronic crossover and biamping, why do we care about matching sensitivity or impedance? 
I still think that 83 is too low, you'd have to drive it pretty hard to keep up,  but you could certainly use anything from 4 to 8 ohm from 87 to 92 sensitivity. 
Based on that, I will expand the search.

you must vent or port your box with this woofer

The Monolith I was ported and the bass couldn’t keep up with the speed of the esl, that why with the II and the III they went sealed, tighter faster except they used that junk cheap driver, I posted it’s T/S here.
http://www.martinloganowners.com/forum/attachment.php?attachmentid=18105&stc=1&d=1437711906

The one Jon Fo used could work Peerless 830699 but it’s FS is much higher (double) that of the SV-12
http://www.martinloganowners.com/forum/showthread.php?16441-ML-Monolith-III-and-damaged-woofer&p=173694&viewfull=1#post173694

Cheers George

Thanks for all the input.  I have reached out to ScanPeak  for more data on the Discovery 30/4558.  Also inbox the guy that had the SV12's for sale,  but haven't heard anything. Even though the post was a year ago, I think maybe he still has them.   I will be putting a sub with the setup,  so I don't need it to down real deep.  Question:  what would be the ideal  crossover point for the ELS  running at three-way?

Even though the post was a year ago

My friend contacted him only 3 mts ago, still had them.

Cheers George

The MMS of the 30W/4558T00 is the moving mass, it’s some 36g higher/heavier than the SV-12 which says to me it’s not going to be as good at 130hz and 1 octave above, fine for below 80hz but the Monolith panels won’t take to that low frequency too well.

Cheers George