Can anyone help me with better phono? Did anyone...?

I currently use Bryston 12b preamp with MM and MC phonos.
This preamp along with this phono is concidered to be the only pain in my analogue setup as well as digital:
J.A.Michell Gyro SE -> RB300 -> Benz Glider medium out...
I cannot realy find a volume position that will satisfy both warmth and details. On the lower volumes before 12:00 there is a lack of bass. Once I pass 12:00 the bass is OK but the upper midrange is getting emphasised and sound becomes annoying if listened for more than 10 min. Pluging in the high output cartridges will not do any better except you'll get the same problem starting from 8:30 level.
What I should start experimenting with?
What is the minimum amount and what brand should I use with my current setup to step away from that problem?
And by the way did anyone used phonos with passive preamp?
Your question is difficult, not knowing the rest of your equipment.

My first thought is to try the Lukaschek PP1 phono stage that was specifically designed to go with your Benz. If that were paired up with the Bryston, you could at least separate ( sonically ) which product was contributing what to the overall sound.

Other phono stages could stand in for the Lukaschek, and any good tube unit should make satisfying mids, with the bass having at bit more of the bloom and output you seem to crave.

Let us know if you make a trial run and what the results were.
The fact that you are having the problem with both your analogue and your digital gear suggests to me that the problem has more to do with achieving a pleasing frequency balance and taming your room acoustics than it does with simply changing your preamp. Obviously, changing your phono preamp won't do anything to improve your digital playback.

It seems that at lower volumes your system is bass shy and that at higher levels room reflections may be coming into play that turn the presentation harsh or bright.

I would experiment with relocating your speakers (maybe closer to the wall) to reinforce the bass, and then experimenting with adding some acoustic room treatments to tame the early reflections in the room. If you still can't get enough bass from your speakers at normal volume levels after repositioning them, then you may want to look for speakers with better bass performance.

Alternately, a tack that may yield surprisingly good results is to relocate your speakers to a wall perpendicular to their present location. If they're now on the short wall, try them along the long wall, or vice versa. You will be amazed at the change in the sonic portrait.

Make no mistake, if you are dealing with major acoustic problems, using the best equipment on the planet will not provide pleasing results.

Happy experimenting!