I don't know whether the sound volume was the same when I tried JRiver, iTunes, Audirvana, Roon, and Pure Music, but to me JRiver in bitperfect mode sounds significantly superior to those other players.
JRiver sounds more like music: richer, fuller, and more emotionally engaging than those other players. The other players sound dull, lifeless, and boring, like digitally processed music.
If there is a "glow" and a beautiful tone in recordings, I get all of that in JRiver, and it is addictive in a good way. I am listening to Mazzy Star right now, and the sound is so beautiful that I am in awe of its gorgeous tone. I get almost none of that sound quality in the other players.
I know that bitperfect is supposed to sound the same regardless of player, but I know what I hear. It's not even close.
Roon has a lifetime subscription price of something like $499. I would pay that price for JRiver without hesitation.