Conrad Johnson SS amps

I am currently looking for a new power amplifier to drive my Martin Logan CLSIIs (4ohm load). I am deciding between CJ's MF2250 and MF2500. I was wondering what the difference was between the the stock model and the "A" model. ie: MF2250 vs. MF2250A. I would also like to know if they can they be bridged? Would I get better results using two MF2250 amps or a single MF2500 amp?
I have gone back from a Premier 11 to MF2500, fed by a CJ Premier14, driving my good old Dunlavy SC-IVs as I value more the dynamics and the low noise level of SS.
Question: there is a MF2300A on a local Craiglist listing, should I consider to acquire that to replace the MF2500 or maybe to use it to bi-amp my Dunlavys?
The only thing I would do with a MF2500 is either send it in for an "A" upgrade to CJ, or send it to Bob and Gary Backert and let them do their own upgrade. The latter certainly did a good job on my aging MF2250.
I have a Sonograph SA-250 (I see there is one for sale on this site right now) and although I have not used it in awhile due to equipment swapping, in my opinion it is a very fine sounding amp.  I believe this is a Mosfet amp.