Just wondering if you have tried the Jeff Rowland Concerto preamp, cause you're using their monoblocks already. The whole system will have a sweet top-end, warm midrange, and clean, deep bass (but not too plumb). For my taste, there're only several brands I can think of (in order of preference), no matter tube or solid-state:
1. Accustic Arts
2. McIntosh
3. Hovland
1. Accustic Arts
2. McIntosh
3. Hovland