Hi Dave_b - Blimey MMs should be good! I've only got Transparent Ultras between CD/pre/power/speaker but Reference power cables (amazingly better than Ultras). The power cables are very full-frequency, and on the 505 it's probably pushing my poor old Sonus Faber Electra Amator IIs to their limits.
I've got Nordost Vishnu plugged in at the moment, and there seems to be less treble flying around, and the mid is sweeter, but the bass & general resolution and image is not as good. However, I think I'm still burning in the Nordost (5 days so far) so I'm witholding judgement.
I still wonder about your original comment of not using networked power cables with the 505, and I'm hoping someone from Absolute Sounds (Krell importer in UK) will give some guideance. I believe your MITs are networked and they're obviously working fine.
I am beginning to think the issue lies with my poor old speakers, but I can't afford that upgrade at the moment! (Amati's are tempting)