OK, catching up… I received the speakers around the first of April. We had guests so I couldn’t work on the replacement for a week or so. The Misco replacements look identical to the Megas in my RM30Ms. I found that the wires to the original drivers had one smaller spade connector needing replacement and the WCF faces were round in shape requiring Dremel modification of the squarer mounting recesses. But they are finally in place and I have watched Birdman and Interstellar at theater volume and am extremely happy with the improvement. My center now sounds like a center should.
The bad news: the drivers ended up costing me $197.56 in all. That is $84.43 per and $28.70 shipping. I completely agree that it was too expensive but am very happy with the result since I didn’t know if I was ever going to find replacements. Good luck, all, I hope you do better!