I own Druids with the 08 drivers, and my Super-T amp sounded good but not great. My experience is that despite the 101dB rating, the Zu FRD needs a bit of power to really come alive. I went from Monarchy SM-70 Pros (fabulous sonics but too noisy) to the Super-T (not enough power) to an Almarro A205A (still not enough power) to a First Watt F4 clone (REALLY nice but not quite enough current) to my current Audiosector Patek, which sounds just right. My only curiosity now is around OTL amps, and I might try an Atma-sphere S30 someday.
I ran all of these with a tube preamp. I never tried a higher power TriPath amp, but it might be worth a demo with the Credenzas. All the amps I tried were under $1,000.
David