@elizabeth I haven't used the BP26 but I have experience with the preamp section of the older Bryston B60, which is pretty much the same as the BP6 which in turn uses the same fundamental discrete op amp circuits as the BP25 and BP26 and shares the same sonic signature. (Bryston says this themselves and isn't shy about showing this in the schematics.)
Based on this experience the Bryston preamp circuit is very musical and nice, but fundamentally colored by the electrolytic caps. There simply isn't any electrolytic that's truly neutral. The old Black Gates were the best sounding I had heard and the recent Mundorfs are very nice (I'm using them in my B60), but they're not anything like film caps, much less straight wire. The funny thing is these caps are often warm and fuzzy sounding once broken in, generally softening the highs and adding fullness (some would say bloat) to the lower midrange and bass. This actually works out great in the Bryston as it balances out any potential hardness/brightness in the op amp circuit, and it also adds warmth that helps make their amps sound better (synergy!). I think if you swapped out the 'lytics for a better film cap that's very fast and clear, the preamp would actually sound worse. Ultimately holistic balance in the circuit/system is more important than absolute correctness of a given part, and this is why it's worked for so many years. It might sound like damning with faint praise but hey, it's your enjoyment that counts!
Based on this experience the Bryston preamp circuit is very musical and nice, but fundamentally colored by the electrolytic caps. There simply isn't any electrolytic that's truly neutral. The old Black Gates were the best sounding I had heard and the recent Mundorfs are very nice (I'm using them in my B60), but they're not anything like film caps, much less straight wire. The funny thing is these caps are often warm and fuzzy sounding once broken in, generally softening the highs and adding fullness (some would say bloat) to the lower midrange and bass. This actually works out great in the Bryston as it balances out any potential hardness/brightness in the op amp circuit, and it also adds warmth that helps make their amps sound better (synergy!). I think if you swapped out the 'lytics for a better film cap that's very fast and clear, the preamp would actually sound worse. Ultimately holistic balance in the circuit/system is more important than absolute correctness of a given part, and this is why it's worked for so many years. It might sound like damning with faint praise but hey, it's your enjoyment that counts!