Firstly a bit of background in case there's an obvious solution I've so far missed. Using Gentoo, Xfce4, and previously was using xfce4-mixer which is now depreciated and the advise is to use the pauvcontrol-mixer instead.
The xfce4-mixer allowed you to add a button to your task-bar which upon mouse wheel up/down would adjust the volume, of a channel in alsa. I in fact edited it slightly, to allow me to add 2 of these controllers, one of my master channel, and one for my line-in channel, which is attached to my PS4. This mean I could control the volume of the input from my PS4, without muting the rest of my system.
Now I've moved to using pulseaudio instead, (infact I've been using it for awhile but the old controls worked so I never looked further), I've noticed that the line-in channel simply seems to not 'exist' under pulse audio. I've gone through all the listed devices and muted them one by one, but I continue to be able to hear the PS4 clearly and the volume isn't effected at all.
Then, I fired up alsa-mixer in a terminal and I can still control the volume for this via alsa-mixer, even though my system is now running under pulse.
How do I get 'all' the control of all channels handed off to Pulse instead of using alsa mixer, and on that note, is there any good 'mixers' that can be used within xfce4 on the taskbar to control different channels?