Not quite; 'pactl list modules' will give me a list of all currently loaded modules, but it doesn't tell you what modules are available on the system to be load

Not quite; 'pactl list modules' will give me a list of all currently loaded modules, but it doesn't tell you what modules are available on the system to be loaded. So you can't use it as a way to discover PulseAudio functionality. For example, in the 7.1 surround example I mentioned, you load the module 'module-virtual-surround-sink' (I followed this guide: https://www.reddit.com/r/linux_gaming/comments/2ot5ov/enable_system_wide_hrtf_with_pulseaudio/ https://www.reddit.com/r/linux_gaming/comments/2ot5ov/enable...). I didn't know this functionality existed and none of the tools gave me a way to discover it. It was only through that linked guide and then later the 'PulseAudio Under the Hood' page discussed here that I found out about it. (as an aside - module-virtual-surround-sink is extremely cool; you can load your own custom spatialization HRIR into it)