My speakers are rated at 86, and is for a small bedroom system, maybe 12x14 feet is size, and has appropriate room treatments. I would imagine anything 25 watts or above would be sufficient.I would go with something of at least 50 watt/Ch for headroom. I have speakers of the same sensitivity in a similar-sized room and the meters on my SS do occasionally surpass the 100 watt mark, and I don't often listen above 90db peaks.
Yes, you can typically get away with less power with a tube amp but that's really only due to their soft-clipping characteristics, otherwise, watts are watts and additional headroom will result in a more relaxed, confident sound.
I had the Cronus Magnum II for a while, it had some audible hum, but otherwise sounded nice with upgraded NOS tubes. I sold it though because I concluded I prefer my 50 watt/Ch Cayin A88T for its greater transparency and dimensionality. Cayin are not very well known but they're essentially the house-brand of the factory that makes Prima Luna. Their amps are built like tanks and have some of the finest point-to-point wiring you're going to find in this price class. Mine was built in 2006 and hasn't needed any servicing other than new power tubes.