I’ve posted the specifics in the ‘95% Solutions’ thread, for the sake of brevity I’ll crosspost here with a summation:
My Koss ESP/95X electrostatic system was not that impressive from the get-go. However I’ve swapped the earpads, added a beefy solid state preamp and Linear Power Supply.
These additions have turned this setup into a synergistic renaissance! They are my go to warm, relaxed, yet much more detailed and transparent than stock setup.