You can find a lot of good info about headphones and amps at the audiocience.com site. Those guys live for measuring stuff, being audiophiles, lol. That's where I discovered the JDS Labs Atom Amp 2. A recent review by them for a new product.
BTW and fwiw, I also purchased a set of Hifiman HE400SE planars for $109 (another audioscience find) as a gift to go with the Atom Amp 2, and those crazy things thru the JDS amp and an Oratory curve are really close to my $1300 Audeze LCD-X 2021 thru custom amp and Oratory curve. I guarantee the mix solution would be no different using either solution. Crazy good for crazy cheap.