catridge match with Morch DP-6

I'm thinking of upgrading my rewired rb300 to a Morch DP-6, and wondering what cartridge would be a good match. First of all is Morch arm a really good one to go for? And then the catridges currently on the shorlist are: 1. ZYX R-100, 2. Ortofon Kontrapunkt B, 3. shelter 501 mk II. The turntable I'm using is J.A. Mitchell Orbe. Could anybody give me some advices please?