tube amp for ribbon tweeters

Offhand, I would recommend one of the Decware Zen el 84 tube rectified models. Some of the older models allow switchable both triode and pentode operation, so you can try both ways to see which way you like better. They also have a volume level, which comes in handy if your active crossover doesn't have one.

WOW! Even new they are very resonable...have you heard it? Sounds (looks) to good to be true.

I have heard one in another system and they sound good. I use single ended el 84 tubes for my foil tweeters, and the single ended el 84 sound the best of many different amps that I tried, varying from solid state, push pull, DHT etc..
The Decware Zen is also not fussy about speaker impedances. You can pretty much sell it for what you paid used anyway, so it is worth a try, I can't imagine needing much more for the high frequencies.

we'll see how it does...should arrive Monday.