Tube Sound Question

Um...good question. I've had a lot of tube power amps. When I went from a sand power amp to a glass one, it was a never-go-back improvement. It's difficult to quantify given the variables. In other words a good set of tubes in either pre or power can be enough to change the ratio. 
What are you trying to do?

I added a tube phono preamp to a solid srare power amp once and it opened up the sound in that holographic way that tubes can impart. So yeah, you could say a tube preamp can give the tubier sound in a pre-power pair. I'm all tubes now so not a concern.