I recently had my MF2500 upgrade to the "A" status and highly recommend it. More detail throughout the listening frequencies especially the midrange for $500 it is a worthwhile upgrade. If you are looking for specifics on the "A" upgrade you can call Knut at CJ and he will be glade to help. I can also send you a copy of what Knut sent me if you give me your e-mail address.
As far as the pre-amp is concerned I believe both are tubed units so I would probably go for the 14 if cost is not an issue. I upgraded from the 10A to the 16ls II and have never looked back. I did own the 17 for a short while before purchasing the 16 and in my opinion the 16 was worth the money. If the 14 offers the same improvement over the 10 then I believe it would also prove worthwhile. Hope this helps.
Chuck
As far as the pre-amp is concerned I believe both are tubed units so I would probably go for the 14 if cost is not an issue. I upgraded from the 10A to the 16ls II and have never looked back. I did own the 17 for a short while before purchasing the 16 and in my opinion the 16 was worth the money. If the 14 offers the same improvement over the 10 then I believe it would also prove worthwhile. Hope this helps.
Chuck