Trying out a tube preamp

Hello, all. I'm looking for some ideas. My 2-channel system consists of a Sony SCD777ES front-end, Bryston BP25 preamp, Bryston 4BSST amp, Audioquest Python and Caldera wires, and Totem Mani2 speakers. My listening room measures about 13 by 15 feet and is "dead" in character -- carpeting, sheetrock over concrete walls, bookcases, etc. Musical taste covers the spectrum.

I'm very happy with the system and have been enjoying it for a few years. But... you know how it goes. Lately I've been thinking of trying something different. I'm thinking a tube preamp in place of the BP25. Just a hunch that it might be a worthwhile change. Let's say the budget is up to USD$5000. Used is fine. Any recommendations on what would work well with the rest of my system?