Tubes, tubes, tubes, tubes, tubes...
Did I mention that I think you need tubes!
Having owned a 4B-ST (now have the SST version) and had Platinum Solos (if memory serves me right similar to AAD - Phil Jones...) some time ago coupled with a Sony cdp (had a stock 333ES, now its modded) I can whole heartedly advise that the introduction of tubes at the preamp stage will do wonders. Lots of good choices - Sonic Frontiers, CJ, ARC and a good bang for the buck is Rogue (I have a Magnum 66).
A Bryston preamp will not solve your problem as they are brutally revealing and hide nothing upstream. I owned a BP-25 so I can speak with some level of experience. So in closing if you want warmth and are not willing to swap your source then look at a tube preamp.