If you need two channels and are looking for primarily keys, for the money of two REDDI, you may consider some extra fire power like the Pacifica... or maybe something from the Neve or Neve-esque family (although Fletcher likes to rant about anything with the "N" wordheh)
I guess we're now getting into the "what's your price range" and what do you want from it" territory.
Like I said, in my experience I love what the REDDI does. And as for your concerns about stacking and multiple tracks, I say go with what sounds the best... remember, entire albums were done on consoles like the Quad 8 or a Neve and I'd take that character any day over a more sterile sound like the Avalon.
The M71 is fine, but perhaps not as much range as some others you may find, like the Pacifica, Brent Averill or some that Fletcher suggested.
Hope that helps
-a