I've been struggling with the same question for years! I go from SS to tube,balanced to single ended,digital display(convenient user interface)to simple controls(no display).I've used a BAT 50 SE,Consonance Cyber 50 and Cyber 222,Sonic Frontiers Pre 1 SE,Conrad Johnson Premier 17&18 LS, and Muse Model 3 to name a few.
At this time I seem to have settled on the Bel Canto Pre 2 and a Rogue 99 Magnum.They have different strengths,and I go back and forth between the two.The Bel Canto is very quiet,provides balanced ins and outs,and has the best user interface I have encountered.It is very musical and stays "out of the way." The Rogue is marvelously dynamic(perhaps even powerful).
Good luck in your quest.