Re-preamp.
I've tried Wadia 27 directly into Jadis JA30's. Not fantastic.
Much better with preamp. More open, more life, wider & deeper image.
Better impedance match?
Jadis preamps do have an "impedance matching" valve.
I've tried a passive preamp: not good. But I must admit I haven't tried the better passives like Audio Synthesis Passion.