Loving my Crack! Aptly named too as you've definitely gotten me hooked on the sound and the hobby. Speedball ordered. Using HD600s and an Apogee Groove DAC.
Regarding rolling, would it be appropriate to add "M8136" and "VX8136C" to the list of 12au7-equivalent tube types? I believe these are additional British designations (if not identical to?) "CV4003". Stumbled across these while researching the codes of a Mullard I bought (full code is 631 R4I3, FWIW).
My kit came with a nice RCA 12au7 and I've also tried a modern Electro-Harmonix (which sounds better than I was expecting for the price and provenance). Can't say I loved the winged C/SED/Svetlana 6H13C I got as a backup for the JAN Philips 6080WC that came with my kit. It sounds loose or rough to me, YMMV.
Thanks again for the kit and the community,
rabele