There will be no stress to the amp, because the amp won't reach full power before voltage clipping. High impedance = easy load.
But voltage clipping will start at moderate volume level, lower volume than with lower impedance speakers. A voltage-clipping amp can damage the speaker with the square-waveish output signal. It will sound truly awful, so you won't miss it if you are mindful. Just be aware that it will never play as loud as 4-8ohm speakers, so don't try. Then just watch out for distorted sound when you turn it up and you'll be fine.
The danger to the amp would be if it were current clipping into a LOW impedance load for long enough to overheat something. With Luxman there would be overcurrent protection scheme - it is an extremely well engineered amp.
75W>8R is probably around 35V rails, so for playing at low to moderate levels you'll probably have plenty of voltage before clipping begins.