I am going to go way out on a limb here and say that from my own personal experience, speaker and cabinet choice makes more tonal difference than anything else and I do mean anything else.
I can run my Marshalls and my Mark III and (when I had them) my Triple Rectos into my Marshall 4x12s with either Greenbacks or G12T75s and it always sounds...Marshally.
I've always until fairly recently only played Mesas through 1x12s with EVs in them.
If I plug a Marshall into an EV cabinet, it sounds more like the Mesa sound I have in my head from so many years of hearing it, than it sounds like the classic Marshall sound.
If I plug a Mesa into a 4x12 loaded with Greenbacks, it sounds more like a Marshall.
The sound of the cabinets and speakers is the dominant factor, making even very large differences between amplifiers comparatively minor.
Yes, different amps unquestionably sound different. But to my ears, speaker and cabinet selection is 70 percent of tone. Amp selection is 30 percent.