Let me say I've never used the RC's, but HAVE played with a whole lot of 10s.
My two favs are the old "Vintage 10" Celestion, and the Eminence 10ALK ( Alnico/Kapton former). They're different toned, but each is outstanding. The old Vintage 10's are still out there if you look for em.
The new Vintage 10 (or whatever C calls them) is "ok" but not as nice. The old ones had a rather in your face attitude, while the new ones are a bit more subdued, less brilliant, and less low end... more Vintage 30 toned, but in a 10 inch size.
The 10ALK (now called the 102 or something like that) is the BEST 10inch Alnico I've ever tried. These are the Fender Blue (when offered by Fender) and are the ones that gave the reissue Bassman a bad reputation. You see... you need to break in the speakers, which nobody who was "evaluating" an amp ever did, either reviewer or customer in a store. Once broken in, they are DEAD ringers for an original 10" Jensen Alnico P10Q. Good speaks they are.
So, dunno bout the RC's, but.. I'm not sure I'd ever look to try 'em either, as the tones are just so good from the two I've mentioned (when used in a 60s/70s Fender type amp that is).