Hum level with Absolare amps

97dB horns with powerful tube amp isn't a good match at all.
You either need lower-powered amp or you need SS amp. Solid states are usually more quiet especially for very sensitive speakers.

I heard Atmasphere amps are very great with noise floor just like solid states, but was generalizing rather than being particular. I also believe that Berning ZOTL amps that are substantially lower in power, but also have great noise floor parameters. I believe that >100dB is the number to go after when dealing with sensitive speakers.