Advice on amplifier and B&W speaker pairing

I know this topic has been covered before, but I’m looking for recommendations on two specific amplifiers and what the optimal pairing would be for B&W 800D3 speakers. The speakers have not arrived yet, but I already own the amplifiers: Nagra Classic Amp and the Audio Research Reference 150SE. I’m guessing most people will suggest that I listen to each configuration, and make a decision myself as to what option sounds best. I’m looking for more technical guidance though. The idea is to keep the better matched amplifier and sell the other. The preamp being used is the Audio Reference GSPre

My dilemma: I adore the 150SE and generally prefer tubes over to SS. However, even though the ARC can push out 150 watts on the 4ohm tap, and the B&W has a sensitivity of 90db - this speaker has a wild impedance curve (3 ohm-20 ohm) and has some pretty significant phase angles. I’m wondering if ANY tube amplifier can deal with these types of loads. Because one must choose the correct tap, it seems the amplifier will never be running in it’s comfort zone. I think my biggest concern is how the frequencies could possibly be skewed at the upper frequencies.

The Nagra wouldn’t have these issues, but only outputs 100W into 8ohms and approx 175W into 4ohm. Considering the 90dB sensitivity of the B&W... perhaps this is the better option?

Setting aside sonic preferences. What do people recommend in this situation? Thank you!