I can remember when I went on a little cannibalising spree a couple of years ago - tried to rip all the RMXP graphics I could get my hands on, and put them into RM2K3 chipsets.
I gave up after about 3.
I have to say, I prefer the RMXP graphics, and they way you can put them into the game, but I prefer RM2K3 as a building engine.