I think the 12ax7 affect the sound quality more than the 6922 for this preamp. In addition to discussing this with Aesthetix, you should also talk to Andy at Vintage Tube Services.
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I have the CALYPSO and did a lot of tube rolling.
It is worth the extra cost to obtain the correct NOS tubes for the Calypso.
NOS "THE" Mullard "12AX7" (rare early square getter Mullard, with the famous, elusive longplates, the first generation of Mullard 12AX7 tubes, 1950s vintage Blackburn factory date coded, significantly better than the famed Mullard 10M gold pin series, at a lower price),
and the Amperex Mini Watt Gold Pins SQ 6922 tubes.
(these are the legendary Amperex/Philips Holland made (have ∆ etched codes) 6922/E88CC premium version gold pins tubes that are considered by many as best of the best 6DJ8/6922/7308 type tubes).
Contact Brent Jessee (do google search) to buy tubes or just great easy going free advise.