You may use a controller application such as Foobar and push music to the Oppo via the ethernet or wireless port (using the player as a renderer) without needing a monitor.
True. I got this to work using Jriver as the player and the Oppo as the renderer. But it was a pain in the a$$ to get it working and keep it functional. I had to use a monitor to set up the Oppo as a DLNA network renderer every time I wanted to listen this way. Then getting the Oppo to show up in Jriver as a renderer could take up to 10 minutes. Once working, track selection, start, stop, skip functions could take around 5 seconds to execute. And this was with 16/44 bit rates. Hi-rez files had to be downsampled to lower bit rates to work. Then to release the Oppo from renderer mode in order to play a disc required restarting it. I was using an ethernet connection for both the computer and the Oppo, not wireless.
I'm new at this DLNA stuff so some of this might be due to my incompetence. My network might not be optimized for DLNA over ethernet, though I never had a network issue streaming music (even 24/192) though a Squeezebox Touch. Based on my experience and what I've read, streaming music via DLNA is not ready for prime time unless your cool with MP3 bit rates. I'm not trying to rain on anyone's DLNA fantasy here, just trying to give a realistic glimpse at what to expect. If someone can get this figured out and working smoothly with hi-rez, high bit rate music files, please let us know how you did it.
I will say that if you can get the PC close enough to the Oppo to connect via USB or HDMI, that works really well and it's what I use all the time.
Russ