I think blind listening tests pretty much say it all. There may be very small differences, but when all things are equal and people cannot consistently identify one from the other that makes them trivial and unimportant, imo. If someone is looking to improve sound quality it is always in the speakers, sub and placement in the room. I don't believe in buying expensive amplifiers to eq the sound. Imo, with a good amp there should be no coloration at all.
If I had a ton of cash and wanted glowing dials and actually quite beautifully built amplifiers in the upper echelon I'd have one, but I'd have my speakers sorted first. That's where the bulk of your budget should go, IMO, IME, YMMV and all that good stuff.