Eddy ...
Why not pick up a used ARC Classic 30 or ARC Classic 60 to pair with your preamp?
Also, if I were you, I'd forget about "warm" or "transparent," and just concentrate on what music really sounds like when you hear it live.
Have you ever seen the original version of "The Wizard of Oz?" That movie was made in the old Technicolor days ... beautiful to look at (warm), but not true to life. Everyone loves Technicolor movies ... but break away from the movie and walk outside into the environment. That's realism.
So, then Eddy, the challenge you have is ... do you want the distractions of Technicolor, admittedly with its unique attractions, or do you want realism like in real life?
I submit that what you refer to as "transparency" is more true to reality, and will be more satisfying over the long haul.
And by the way, as an owner of an ARC Classic 60 for over 30 years, I can tell you that it has its own special musicality. Not near as "transparent" as the ARC REF amps of today, but addicting nonetheless. And the ARC CL 30 is even a little sweeter sounding than the ARC CL 60.
Happy listening ...