gdnrbob
testing some speakers with the MA-1s when I got them back in 2011, I found that speaker ohm should be more than 8. 12 or 16 is fine, along with a "nice" amp loading and 90+ sensitivity. Yes, the amps will drive 8 or lower ohm speakers also, but you are not getting what you paid for. The OTL factor comes into its own with matched high ohm and sensitivity speakers. I tried Speltz autoformers, very capable, increasing the chance of speaker match, but all in all a minus compared to "easier" speakers driven directly by the amps.
Yes - the AK Dream Makers, 16 ohm, 92 db sensitivity, are a very good match with the MA-1s. From what I've seen (not heard them) the Vandy Treos are a poor match,
https://www.stereophile.com/content/vandersteen-audio-treo-loudspeaker-measurementsWhat about looking for some not-so-expensive high ohm speakers, just to test the concept - or borrow some, from a shop, just to try?