Amp & Speaker matching

There is no danger at all with using a speaker of ANY nominal impedance with any tube amp. Your use of even higher impedance speakers than the common 4 or 8 ohm speaker is particularly ideal with tube amps--any possible frequency response variation caused by the typically higher output impedance of tube amps will be lessened when used with such high impedance speakers.

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.

Not sure I agree with Larryi.

The output transformer in a tube amp reflects the load impedance back to the the tubes. If you use speakers rated at a higher impedance than the output transformer impedance things will be ok. You will just get lower output.

If the speaker impedance is lower than the output transformer impedance then the tubes will draw more current than if the impedances were matched.

Whether or not this is a problem depends on the amp's design limits. Consequences range from none to damage such as blown output transformer, blown tubes, or worse, depending on amp and the amount of the impedance mismatch.

Check with your amp manufacturer for advice.

R Burke,
In my opinion the higher the speaker impedance the better for tube amplifiers,i.e. easier load to drive and generally less distortion. You should not have any problems.Low impedance speakers can be a 'potential' problem for some tube amplifiers.