I had a constant low-level hum both mechanically (transformers) and through the loudspeakers from my Cronus Magnum II. I tried everything under the sun to reduce this--I documented some of my experiments a double of years ago on this forum. Nothing worked, no different wiring, power conditioners, earthing, etc. etc. etc. I really like the sound of the CMII, but I ended up listening for the hum during the really quiet passages. So it had to go.
OP: I'd look at Backert and Raven, or perhaps tube preamp + SS power.