Answer: ignorance, wanting a super simple system, and being a 'certified' computer dummy (so I have no idea how to setup/maintain a NAS). I thought the ethernet input/streaming function built into the DSJ would provide SQ improvements with a 'plain' server. Now I'm confused at all the options and reviews out there.
Understood. I just reread your original post. Since you heard no difference between the server vs the Mac over usb, it's probably not going to be worth spending more money on high end computer audio. The gains made for the things you listen for will probably be minimal. It also sounds like you only have a wireless network point in the audio room? You would need a hard wired connection for the DS Jr to attach to the network.
The original way you started, Macbook to DS Jr via usb may continue to be your best option for ripped files, and perhaps something like the Node could be used for streaming content.
It's been my experience that many of the audible differences and "improvements" in SQ offered by upgrading servers, renderers, and network audio are much the same as say those obtained by upgrading to NOS tubes, vibration control, or careful selection of cables. That is, more open vivid imaging, blacker background, and more tactile engagement. I've read enough of your posts here to know you aren't a big fan of that part of the hobby. No flames. You're what I'd call a meat and potato Audiophile. Cooked properly, it's a great experience, and there's no Salmon foam.
Happy to discuss it further via pm if you're interested. This is a review thread after all.