Best high-efficiency speaker under 10K
Being high efficiency, and easy to drive more times than not, go hand in hand with some form of colouration.
I can think of one with high’ish efficiency and easy to drive, that would be the some of the TAD speakers that to me sounded uncoloured.
https://youtu.be/Fai7Pnw1c-Q
https://youtu.be/swgPaVlE-0E
https://www.stereophile.com/content/tad-evolution-one-loudspeaker
Cheers George