celander, no, you are not missing anything. You said, "But I’m less certain that a SM assembly having a mixed set of IC’s would be terribly revealing as to which IC was responsible for the effect in SQ. " It won't. He's just having fun. Mixing cables is fun because the results are fairly unpredictable, but it does not allow for an efficient way to propel the system toward a given set of sound attributes.
Tonight I am putting in a different set of double ICs, even though the system sounds wonderful. One simply does not know the limits of change with gear on hand until all permutations are tried. I just did a comparison once again between using the software volume control on ROON versus the digital volume control of the Exogal Comet. No comparison; the Comet's vol. control quality destroys that of Roon. Anyone using Roon with the software's vol. control is giving up a LOT of sound quality. The only time I would use it was in a config. with a dedicated DAC direct to amp. And, frankly, putting in a dedicated pramp and another set of Interconnects might still be preferable; that's how poor the Roon software volume control is.