Right, the Spatials can be a difficult load, as can most full range speakers due to impedance swings. Many people just look at sensitivity and think “high sensitivity equals tube amp friendly”. But as you see, that’s not always the case. PP tube amps do best, SET amps do worse and OTLs do the worst with difficult speaker loads. SS amps will almost always be a better match for speakers that are not an easy load. There’s a ton of good SS amps out there and a few good digital amps, all would be good choices here.
Oh and I agree re: the LIO - that is an amazing piece of gear. Vinnie knocked it out of the park with that one.