"Oppo will play WAV, not AIFF." That is not correct. I owned an Oppo 105 and 105D and both play AIFF fine. I did this using the digital inputs on both the front and the back with no issues. Seen many other Oppo owners do the same.
What do you mean by "monitor"? Hardware, software? The only monitor I know of is a pair of small speakers used in a studio.
For mac music software, Audirvana+, Amarra & Pure Music are the top ones. You can trial them all & decide for yourself. JRiver was made for Windows, and just recently released for Mac to mixed reviews. I haven't heard it so no opinion. Cheers,
Spencer