One thing you should keep in mind bewteen the B and C versions is what that difference in output tube means.
The 805 - I own the B with a switch to let me also use an 845 output - sounds mushy with the stock Chinese 211 or 845. To have the amp sound good you really need NOS tubes; in the case of the B, GE211's are fine (@$220 matched pair) and sound MUCH better (I have RCA 211's but they are quite hard to find; the GE's were nice too and are relatively easy to find). BUT, the C version, to NOS retube the outputs, requires an RCA 845 tube and that is going to set you back $600 pr, assuming you can find a matched pair! So, if you get a C, you are stuck with the stock 845's, while with the B you have more latitude to increase your amps performance (a B version with GE211's blows away a stock C version IMHO).
One thing to check when looking at 805's is to remember that the B version came stock with Cetron 300B driver tubes - which you really must replace with WE300B's to hear what the amp is remotely capable of (on used market new production WE's are $495 matched pair from a dealer unloading stock). The C version comes stock with WE's. Try to find an 805B where someone has already replaced the drivers with WE's (they have 40K hr tube life so no worries there).