Well, you're doing yourself a disservice then. Progressive players are advancing at a very nice rate, and since the present players are all annoying in some way or another, you might regret not waiting.
The RP56 does not have the chroma bug. However, the RP56 has the very annoying flicker bug.
The RP56 does not have any sort of scaling functions.
The RP91 has some weird quirks as well, but supposedly nothing major.
If I were you, I'd wait for some of the newer models coming out from Denon...