In my opinion "brightness" was a problem with pre-ST Bryston products, not with the ST and SST series. If you're happy to use a 14B or 7B SST monos for power, I believe you will be most satisfied with a BP-25 for pre.
Before I traded in my BP25MC and 7BSTs for a Krell KCT/400cx combination connected via CAST, I experimented with a couple of tube preamps at home with the 7BSTs, most notably the cj premier 16 and 17 preamps. Compared to the Bp25MC, there was a much sweetend sound, softer in the highs but in no way diminished. The soudstage was better overall with the same amount of width but with a better front-to-back definition. The downside of this was that I had to do the comparisons with my CD player, cj preamps and 7BSTs all together between the speakers because I couldn't run long lengths of cable between the preamp and the monoblocks as I had set up orginally in my home. The cjs really made an improvement over the BP25MC with the 7BSTs so feel free to seriously consider alternaitves to the BP25. Bryston makes a good preamp, but in my case I was looking for greater resolution and it was clear that the 7BSTs benefited from a better pre. Happy Hunting!
You are about to get some sound advice, in my humble opinion (pun only partially intended), but this advice is only for the case where you go with ST amps. My first dealer told me that there was special synergy between the Bryston ST series amps and the fairly modest ($1,700 list price) Audio Research solid-state (MOSFET, actually) LS-3 preamp. On his advice and my ears, I bought a 4B-ST and the LS-3. Eight years later, I have owned Jadis, CAT, Hovland and Rowland Coherence II preamps, the latter now anchoring my main system. But the LS-3 is still in my second system (with Rowland Model 6 monoblocks). The LS-3 truly sounded GREAT with the Bryston 4B-ST. In fact, at one point, I was running the LS-3 and Bryston with $10,000 worth of Kimber Select all-silver IC's and speaker cables -- it was only at that point that I heard just how good those components sound together. So my advice to you is to buy a clean used LS-3 (they only cost $600 used) before you drop big money on something else. Make sure you keep it powered up 24/7. Run your best source component through the "Direct" input on the LS-3 ("direct" is a hot-rodded input that only passes through the gain stages and volume control). I do not think you will be anything less than thrilled. I've had a lot of different systems and believe that synergy is 9/10ths of the game -- your question suggests that you appreciate synergy as well -- try the LS-3 if you buy ST amps.
This advice is for the ST amps only. If you do the SST amps, you're on your own!