I switched to a tube preamp using some great NOS tubes that rolled off the highs a bit, but still sound very open (RCA Blackplates). Strings were finally sounding very natural, and it was now easier to tell which cds were poor recordings.
Get better equipment or roll off the highs.
The problem with massed strings (and probably massed brass instruments too) being too overbearing often has little to do with frequency response and a lot to do with distortion. Solid state electronics have less distortion than tubes, but what distortion they do have is percieved by the ear as brightness and harshness and this is why tubes are still around decades on after becoming 'obsolete'. Tube distortion is simply less irritating.
Digital has its own distortions (known as 'aliasing' since the digital industry does not want to admit to having distortion) which is also perceived by the ear/brain system as brightness.
Tube preamps might well have the same bandwidth as a solid state preamp but not sound as bright/harsh simply due to this distortion issue, since the ear converts all forms of distortion into tonality. The reason the higher ordered harmonics (which contribute to brightness) cause this is the ear is keenly sensitive to them as it uses them to sense sound pressure.