Not quite apples to apples to the CMII, but I own a Stereo 100, driven by an RP9 preamp. I’ve gone through many combos of NOS(ish) gain and driver tubes in the ST100, and have settled on CBS 7729 (uber quiet wide bandwidth 12AX7 type) as gain and 7730 (uber quiet neutral 12AU7 type) as driver. This combo is hugely dynamic, extended on both ends, and adds very little coloration of their own. Beats any European (Amperex, Mazda, Telefunken) combo I’ve tried. The Amperex med grade 12AX7 + 7316 are a close 2nd I’d say. I did not like Mullards in there, as they were too veiled, almost "phasey" sounding in treble. RCA black plates in the ST100 are excellent, but do "fatten" up the sound just a bit too much, although that is good for some music. 7729-7730 are the winners overall. I suspect the CM will respond similarly. These 7729 are worth the hunt if you can find them. Easily my favorite American 12AX7 type tube.
