I had recently purchased a Bryston BP 25 and 4B ST and thought that I was in music nirvana.
Then my friend asked ..why don't you try a tube preamp with the 4B ST.
I was able to audition,in my own home..in my own system..
a Blue Circle 3.1 and let me tell you ,my BP 25 never went back into my system. The improvement ..well the only word to decribe it is..WOW..
Granted this preamp is about twice as much as the BP 25 but the improvement is worth every penny.
Blue Circle also make a entry level preamp BC21, which there are a few for sale on Audiogon.
I don't think you can go wrong with either a Rogue or a Blue Circle..
I have since sold my BP 25 on Audiogon..
Happy looking and listening....