Some smart people on here. If this were me (and I've owned 5 pairs of Thiels), I would first install a top end tube preamp.
My first 2 choices would be the Aric Audio Motherlode XL, and the Don Sachs/Lynn Olson Raven preamp (built and sold by Spatial Audio). I happen to own the Aric Audio Motherlode XL.
I'd also throw in the Supratek Cabernet or Cabernet DHT, Backert Labs Rhumba Extreme 1.4, and BAT VK-80.