Are you looking to replace the BB as well? I believe the RPM cranks use a 103mm jis taper? If this is the case, you will need a new 110mm BB ($20) to run the IRO cranks. I'm not sure what spindle length the pake cranks require. You might also consider the sugino RDs, which would work well with your present bottom bracket (assuming you can find them with the proper chainring).

FWIW, I have been using an IRO crankset and BB for about a month with no problems.