My inclination would be to skip the cherry (even though it's already paid for) and use the same molding throughout. I don't see any graceful way to transition between the two.

Are they going to collide? Is there going to be a frieze on the cabinet so the crown ends up at the ceiling? If not, then I guess you run both crowns independent of each other. If they do collide, Run the cherry crown first, all the way to the corners, and cope the room crown to it so there is a perfect transition at the corners; I picture the cabinet getting two pieces of cherry crown, one long and one 12" return. I'm guessing that the room crown is a larger molding with a completely different profile. This means that the carpenter will have to skillfully cut away the negative profile of the cherry crown from the white crown so the two would form their differential union.
Casey

Hello,

Thanks very much to Casey and Jon for the suggestions. Both are "contenders." I've attached a photo of a third approach suggested by my brother-in-law, who is showing off his photoshopping skills (he installed a couple of cabinets in photoshop for another question we had, but installing crown in photoshop is just scary good i.m.h.o. ;)

Chris

And yet another photoshopped option... place your vote now! ;)