Martin Logan Summit X with Cary Audio 805ae

I would not expect that combo to work. Some high power tube amps may work depending on their design. Which do you allready own?

What is the efficiency of the Summits? I don't own Summits but own Innersound Kayas and know low powered tube amps don't work exept at low volumes. Innersounds electical behavior may be completely different though.

You might want to post this question at martinloganowners.com.

I looked up the specs on Martin Logans web site. The recommended amp power is 20 to 600 wpc.

If you can find someone that is satisfied with 50 wpc tube power and their room is the same size or larger than yours you may be safe. I would personally error towards the upper wpc limit.