Sorry, just finding your responses weird. An FRFR is not "the type of speaker that's meant to have a band mixed in it". Whatever you play, when you're in a band, there will be a band mixed in to your sound. All an FRFR is, is the sound of an amp through a mic'd up speaker cabinet.
You don't want to guess what other instruments will sound like in the mix? Ummm ok, but again whatever you play, other instruments will be in the sound unless you're playing solo.
You seem used to valve amps - that's cool, stick with it.
Sorry, but denying that volume has an effect on a sound is scientifically wrong. You prefer valve, that's cool.