I am making some progress...I think. I discovered the API calls under Wifi Devices. The Wiim Amp Pro has an API interface. Problem is, however, it only accepts http calls via port 443. The SofaBaton does not support https. It will only make an http call, so certificate acknowledgment becomes the issue. I can hit the WiiM via a web browser and get an 'OK' back with the commands I'm using in SofaBaton.
So I've been playing around with http-https proxies. http-proxy on Node.js is the one I'm trying now. I've got it relaying http commands as https from the browser, but the SofaBaton commands are not hitting the Proxy using the exact same url command. Bizarre.