"Or do we have to contend with matching and esoteric judgements such that 1 power amp will help a pre or conversely screw up the character and quality of the pre?"
improving the power amp or the pre can help improve the sound . that's where the fun is , I have upgraded my poweramp a great deal and can use modest pre amps with it to great effect
"Does it have to be quad matched pairs or can anyone suggest a general workhorse? What would happen if a valve pre and SS power was mixed?"
lots of people use valve pre amps and ss power amps to good effect as I have done in the past
ou might slip, you might slide, you might
Stumble and fall by the road side
But don't you ever let nobody drag your spirit down
Remember you're walking up to heaven
Don't let nobody turn you around
… Walk with the rich, walk with the poor
Learn from everyone, that's what life is for
And don't you let nobody drag your spirit down
Eric Bibb