Wow, what a fun topic. First off, tubes are less important than the output transformer or speaker(s)/cab for determining the overall tone of the amp. Voicing an amp is best done from the back end of the tone chain towards the front. Start with the speaker first. Why? because it's easier to change out than the output tranny...Because if and when you change it out for a different make or model the amp will sound different and the tubes you had in it might not sound like what you are going for with the new speaker.
As far as output trannys go, I have switched out output trannys more than once in my old silverface Fender Champ, and it was incredible how the change affected the tone. It's a pain in the butt to do that so that's why almost everybody ignores the output tranny. Too bad.
In my 2/12 Maverick the stock speaker is a Celestion vintage 30. They sounded dark at low volumes and too bright at high volumes, and with two separate preamps there are a lot of knobs to tweak for tone. Me no like tweaking, like to set and leave alone soft and loud. So I tried some different vintage speaker combinations, some were mismatched brand pairs at 8 ohms in series for 16 ohms, some were 16 ohm speakers parallelled for 8 ohms like the stock Vintage 30's. Each time I changed out the speakers I swapped out tubes til I got something that I liked. I noticed that vintage alnico speakers had a bit smoother edge to their dirty tone and sweet sparkle on the clean, and were more consistent in relative bright/dark balance low to high volume then the Celestions. I'm keeping my secret vintage weapon speakers a secret unless a following post specifically asks, besides, no one would believe me anyway.
I have matched el84 quads of RFT, JAN Sylvania blackplate, GE, Mullard, EH, and Panno (Russian Military) 6p14p-ev. These Russky military tubes are the "Harma" el84's Watford Valves in England sold for their super premium el84's. They are rated for 400 volts like the e84l and 7189, rated for 5000 hours and are happy in my 375 plate volt Mav, I had my choice from the tube vendor when I won their auction so I had him burn in and match at full voltage three very high current draw quads. To keep them from running a tad too hot in my class A power section I sub a vintage Sylvania 5v4, or GE 5v4 instead of the Sovtek/Mesa 5ar4, the tone is a tad darker and smoother and the tubes run a bit cooler. Have hundreds of hours with no problems whatsoever. Speaking of tone, compared to the Mesa's Sovtek these tubes are significantly fatter and richer sounding, particularly when pushed. I found the EH's to sound (very surprisingly) similar to the spendy Mullards, so their claim of being Mullard copies works for my ears. The RFT and JAN Syl blackplates have more sparkle, and the GE's were lacking bottom, brightest of all on top, and ran a bit too hot.
For preamp tubes I have a few of almost every 12ax7 ever made, period. It took a couple hundred auction wins on ebay for me to obtain my collection, and I used a vintage Fender Silverface Champ with a 10 inch speaker crammed in for my tube rolling, only one preamp tube in that amp. Also have some premium 5751's by Tungsol, Raytheon windmill getter, Sylvania, Allied/Tungsol and a bunch of vintage old stock American and Euro 12at7's as well.
I encourage those interested in obtaining their PERSONAL SIGNATURE TONES to wean their purchase choices away from current production tubes, and to DIVERSIFY and EXPERIMENT!
The Euro 12ax7/ecc83 tubes such as Mullard, Amperex, and RFT are the secret of the old school Marshall preamp sound, the Raytheon blackplate and Sylvania long blackplate 12ax7 are faves for the blues tones they produce, and probably my favorite 12ax7's are the old stock Tesla e83cc/ecc803s for following a first position tube, and old stock Siemens ecc83 and the e83cc. Either Siemens "out mullard" the Mullards and Bugle boy Amperexes, deliver a fat, rich harmonically incredibly complex clean and a smooth, complex, dirty tone that has to be experienced to be believed in V1 or first position. The longplate Siemens has less lower mids, which are huge in previous mentioned ones. I use a Canadian Marconi long blackplate in V1 in my Maverick currently. The v1 and v4 are for the clean channel and the v2 and v3 are the dirty in that amp. This is too long already, must stop. Peace.