Preamp choice

You might try a tube pre. Tube pre and solid-state amp have, I've found, the best combination of warmth, accuracy, and bass power.

I have a Conrad-Johnson tube amp connected to my Audio Research 100.2 solid-state amp. Best combo I've ever had from a list of gear that's pretty long.

Tubes,had you thought about the PrimaLuna?

I owned a 4B and 7B's for nearly 10 years (upgraded to Rowland 2 years ago). I had great success with, in order:

Sonic Frontiers SFL-1
Melos SHA-Gold
Rogue 99 (non Magnum, later upgraded to Magnum)

But I think if I were in the market now, and I still had the 4B, I'd look at the Modwright 9.0. It's a great sounding preamp at a very reasonable price. You will want tubes in the preamp, and at that price level, choose a designer who is designing around reliable readily available tubes -- and not one who is running a nice but noisy tube too hot.

Good luck

Rich