Well I have the mid Mono Amps and use the New KLH 5 speakers to more than sufficient volume but my room is not as large as yours. The KLH speakers are rated at 90db efficiency so I would recommend you look at the efficiency rating of speakers and try to get something 90db or higher. You can find a used pair of them for under $2000 and are really good bang for the buck and would fit in your space I suspect.
Consider that the space you plan to put those speakers dictate a rectangular speaker to fit on the shelf. That eliminates "tower shaped" floor standing speakers. Try to get speakers that have at least 10 inch woofers. If you place those speakers up where you have indicated, you will not have as much bass as if you had the speakers on the floor and closer to the corners of the room. Recommendations for JBL and Klipsch are worthwhile as they are generally efficient. Something to consider is the Mid Mono amps put out 40 watts with the EL34 tubes. However, you can also use 6550 or KT88 tubes in the amps and with those tubes you will get 10 more watts of output and those tubes will have better bass than the El 34s but with less pleasing midrange.
A poster suggested AR2x speakers and had posted a picture. I had those speakers back in the day. They are not that efficient and would not be the ideal match for your amps IMHO.
Finally consider that most tweeters in speakers are fairly directional and it is generally best if your ears are at the same level as the tweeters. Since your speakers will be up high, and you will probably be sitting in a chair with your head much lower, you will need to find something to prop under the back of the speakers to angle them downwards to get the treble to sound decent.
If you consider mounting the TV to the wall above the fireplace, you could have speakers on the floor and that would open up many more speaker choices and better speaker placement and Jerry, Bob, and the rest of the Band would play on much better. BTW, the Grateful Dead’s wall of sound, designed by Owsley, was all tube amps and JBL speakers.