Sorry for the late reply boubou. I'm glad to hear that you also ran dedicated power lines to av gear - this makes a tremendous difference in the quality of the sound and video that you're getting.
Of the various brands of cables that I've listened to, Nordost is definitely the one that provided the biggest improvement in sound. I'm actually thinking of upgrading the power cables in my systems to Nordost in the next few months (particularly my 2 channel system).
If you're thinking of upgrading the power cord of your MRX receiver perhaps the Nordost Vishnu would be a good choice:
or a cable from their recently introduced Leif line up: