Newbee, have you looked at the Atma-Sphere amps? You're comment:
"I'm still looking for a tube or ss amp which has the best of both designs, that has warm, full, tight low frequencies with natural mids and highs allowing for great detail with no thinning or brightness."
is exactly what I found in the Atma-Sphere MA1's. I was completely stunned by the bass articulation they provided to my Magnepan MG3.6r's, a speaker that most say can NOT be driven by a medium powered tube amp, much less an OTL. It truly was a revelation! The mids were gorgeous and the highs as airy as I've ever heard...really made me appreciate the Maggy ribbon tweeter, something I wasn't fully able to do when they were powered by my Parasound JC1 monoblocks.
Ulf, I do think good tube amps can provide better bass. Six or seven years ago I used Manley Neo Classic 250 tube amps with Avalon Eclipse speakers and I found the bass more natural than with my previous Levinson SS amp.
I spent several years living in Soulard (St. Louis area) and listened to live music at least 4 times per week. The Atma-Sphere's, and to a lesser extent the Manley's driving the Eclipse, provided a much more realistic upright bass. The way an upright bass projects out into the room is not a start/stop affair...it's hard for me to describe it...maybe "expansive". You get the initial transient followed by this ballooning of the fundamental and it's harmonics. Oh heck...my language is horrible...wish I could describe it better.
Good luck!
Jordan