After living with my new Powerzone 3 for a couple of months, I've become inspired to add my two cents to this thread. It replaced my Shunyata Everest 8000/T and Omega XC PC, both of which served honorably in my system for 5 years. I have the Grimm MU1 driving a pair of Grimm LS1be's. Part of the appeal of the self-contained system is it offers very little daylight for tweaks, like new interconnects, DAC, amp, etc., or other expensive audiofool impulse purchases. But, hey, tweakers gotta tweak at least once in a while, and the PZ is easily the most amazing one I have ever encountered.
I won't belabor descriptions of the magic already well documented here. But there's one dimension that has really taken me by surprise: low level resolution. Ever since encountering volume knobs on electronics in early childhood, the pattern has been consistent: the "presence" of the music just evaporates as the volume gets lower. That is no longer true with the PZ in the system. In fact I find myself being drawn into the music even more. Somehow the magic is even more enveloping. Maybe it's a bit of an exaggeration, but to me it is like the sonic equivalent of defying gravity. Given that I live in a condo with apartment neighbors, this is especially valuable.
I'll add one more unrelated tidbit. I purchased the Lessloss Stellar Entropic PC to feed the PZ. It easily bested the Omega XC, which also had the requisite c19, 20 amp termination. I didn't compare it to any other PCs, but at $2k and change, it seems like a good deal. Interestingly, I tried a Lessloss cable to connect the PZ with the MU1, and got different results. The incumbent Shunyata Alpha PC sounded better.