I tried a set of 7b3 monoblocks in my system at one point in time. It turned out to be pretty good after an internal fuse upgrade, but the overall sound was thin in bass, midbass, midrange. I would pair this with a very thick sounding preamp with heavy on the midrange texture and warm slow bass.
This is my experience also.I did not work together with audio research ref3 preamp
Thin and bright sound.Things improved with onkyo p3000r preamp