Maybe I missed something but I thought FRFR speakers were used so that the tone you get is all Axe rather than artifacts from the speakers.
So why use a tube based power amp such as the fryette 2/90/2? Won't it add a bit of character clouding the tone from the Axe unit?
As a tangent I happened to be in a pawn shop and I saw a solid state 600W stereo power amp. Could that be used as the PA for an Axe or similar item?
I don't own an Axe but just curious.
Because it sounds good to you. That's all the justification anyone needs for any piece of gear.