I stream (or rather download from streaming services) exclusively, and the 507 doesn't do high-res from streaming apps, unfortunately. Then again, Apple doesn't offer high-res files, unlike Tidal or Amazon, so I'm not missing anything.
That said, I've always found the sound characteristics of a player or DAC generally outweigh any differences between a well-recored non high-res track, and a well-recorded high-res track. Meaning if I prefer the sound sig of one DAC over another, I'll prefer a good standard track on the favored DAC over the same track in high-res on the other. I happen to really dig the Sony sound... So while it's a bummer I can't listen to Amazon UHD tracks in their intended quality on the ZX507, I still prefer them on this DAP to how they sound on, say, the Mojo in their intended quality.