I love my bi-amped Khorns, bought them new in 1978. I use a Mac 250 transistor amp for the bass (transistors are better for bass) and I swap between 4 different tube amps, (2 single ended, 2 push-pull) for the mid/highs. You will need an electronic crossover. I use a Crown VFX2a, works perfectly.
You said you want speakers that disappear into the room. My set up will do it. There is no better sound in the world than a properly powered pair of Klipchhorns. Both single ended and push-pull tube amps work well. Overall, I prefer single ended.
Lastly, you have the perfect room for this setup. Large area, tall ceilings.
Good luck. Enjoy!