Matt
Even the unnamed Russian (I think) 6AS7 tubes provided by Glenn for free sound good already on my Darna. I could be happy with whatever tubes I have (rolled) on my Darna. The amp is that good. Rolling different tubes provide somehow different flavours and degree of refinements.
The 6AS7 tubes, IME, have wider soundstage and more energetic highs. The 6BL7/6BX7 have more intimate stage bu hit harder which is very good for the HD800SD.
I find the mids of the HD650 shine more with the 6AS7 tubes especially with my Bendix 6080, TS 7236 and of course the insanely outstanding GEC 6AS7 (mine are Haltron rebranded) brown base.
After a year and a half of rolling different tubes, my opinion of how these different tubes sound did not change.
Of course this is all IMO/E and YMMV.