Recommendation for a highly resolving amp


I have Don Sachs 2 tube preamp driving Pass Labs X350.5 driving Sound Lab M545 ESL speakers. I like the sound very much, but when I went to hear my friend’s Spectral system (driving Quad2912 ESL) I realized my system can benefit from having a higher resolution amp. Spectral amps need all Spectral preamp/cabling, which would be quite expensive. What would you recommend?
128x128chungjh
Chord’s Ultima line is very resolving. They have also addressed historic brightness issues and these are more neutral than the old CM line. They also deliver big power, run cool and don’t take forever to sound good.

I would also look at Boulder and Constellation.  I sell Chord and am very familiar with their line.  I have no affiliation with Boulder or Constellation.  
I don't know your budget but a Luxman m-900u is a solid contender. Very resolving but never neutral or dry.
@chungjh   are you sure the issue is with the amplifier and not with room and speakers?  
or possibly the preamp or preamp tubes?
have you tried different tubes for the sachs preamp?  
most 6SN7s can be overly smooth.  
just trying to help you avoid chasing the wrong dragon.