RCA black plate 12at7 and 6201 offer a harmonically richer sound (I use 12at7 to drive 2A3's).
Mullard Blackburn production is also good for such.
Avoid Sylvania and Eastern European 12at7's as they are leaner/brighter (I also include Mullard box plate CV4024/12at7's from the Mitcham factory in this group).
For input/gain "12ax7's" (which your amp uses) I seem to always end up preferring Amperex Holland (the less expensive 60's short plates are still reasonably priced and their sound quality is up there with the older Holy Grail versions).
Google "Brent Jessee" to view his current inventory/pricing and specifically check out his damaged and rebranded label offerings if you do not require pretty tubes.
DeKay