I wonder if you ever tried tubes: (preamp, and/or amp) with those very efficient speakers.
I bet my Little Luxman Integrated SQ-N150 (10 wpc at 6 ohms) would sound great with those speakers. When I bought it, I drove my Main System's Horns/15" woofer (similar efficiency to yours) with it for a while, but it's purpose is to let me use tubes in my small office without too much heat.
https://www.luxman.com/product/detail.php?id=33
Live close enough to have me bring it by, I'm in Plainfield, NJ, 07062

