The higher the impedance of the speaker the better the match with most tube amps. The "natural" output impedance of tubes is normally high and tubes don't dump current as easily as most SS amps.
The answers to your specific questions are, the output by the speaker will increase, and not be reduced. Niether the tube amp, nor speakers, will be damaged by the relatively high stated nominal impedance on your speakers.
The answers to your specific questions are, the output by the speaker will increase, and not be reduced. Niether the tube amp, nor speakers, will be damaged by the relatively high stated nominal impedance on your speakers.