I can't see why there should be a problem. The MMC4 will actually have a slightly lower output that a normal MM cartridge. I was going to lend you a new cartridge but customs to where you are prohibit this from being a sensible solution! 

Your Creek Destiny apparently has different levels of amplification. The manual says that the preamplifier part of the Destiny should only be in active mode if the source level isn't high enough. You can even adjust the level of amplification, in active mode, at the bottom of your amplifier, but first you need to find out whether passive mode is adequate.

Peter, thanks for looking into the cartridge loan! I run the Creek in passive mode most of the time and everything sounds perfect w/ all other sources. Since the 640P is new, I'll get a replacement for that to completely rule out a defective preamp... assuming the preamp is not the problem, guess will then make the decision btwn cartridge replacement or getting a completely new TT. Will post back once I have more info &/or resolution.