I just received my MX-R amps back from Ayre post upgrade. The upgrade is unbelievably apparent. With just a few hours of running the most noticeable improvements are in dynamics and bass. The soundstage has widened as well. I am finally hearing what Wilson X-2.2 bass is capable of. Associated equipment is Ayre KX-5 preamp, Ayre QB-9 DSD, and Shunyata Zitron cabling. I highly recommend the upgrade. It's really shocking how much more dynamic, clear, and powerful the sound is.
I recently got my VX-5 - now VX-5 Twenty - back from Ayre and am blown away by the increased control of bass and wonderful musicality. I can't imagine purchasing another amp...until of course I pick up the MX-R Twenty!