Gunbei, in all honesty, I won't know 100% until I get the jrs broken in completely, but I will say that so far I am extremely pleased. Until I ran the tar out of them for a good 50 hours or so, they sounded pretty course and restrained. Out of sheer laziness, the break-in is taking longer than it probably could. I'm using the SS amp for break-in duty during 'busy' time to preserve precious NOS stock, and patching in the 60 during 'happy' time. They are coming along nicely, though.
Impedance/level mismatches have been non-existant. FWIW, I'm running both sets of full range outputs from a 5i into each of the amps (the 5i is being fed by a D5; analog front end to follow soon...)
Soundstage width is breathtaking, depth & height are good while not stellar (I'm hoping for a bit more from the midrange as they approach completion of the breaking period and I refine their positioning), dynamics will downright scare the pants off you with a good full orchestra piece!
To quote a famous fast food slogan: "I'm lovin' it!"