Thanks for all the advice!
I managed to get the power supply part all wired up and mounted, grounds included.

- White wires: Power and Signal grounds into the X2-RC filter
- Orange wires up front: B+
I found out that the line filter housing has a good connection to the back panel already, so I just scraped away the anodised layer from the other panels and made sure the continuity was good foor the entire case.
I used the RC filter as the common point for the power and signal grounds. I'll trim and route the signal ground once I have the actual signal bit done. The output transformers have a solid copper wire between pin 8 on both to act as gathering point for all the signal grounds.
Under the motto "Ask thrice, solder once" I do have another question:
Can I just use pin 9 as a "ground" point on the socket and hook up the grid resistor and the ccs straight to that? Maybe even use it as the gathering point for the entire channel?
(the grid resistor and the CCS aren't soldered in place yet)

This would let me hook up most things on the top panel and cut down the wiring I have to drop down to the body of the chassis quite a bit.
I would then have a "left ground", "right ground" and "output ground" meeting up on the copper wire bridging pin 8 on the output transformers, which is where the white wire to the X2-RC filter connects.
Attachment:
IMG_20190303_224153_small.jpg
I hope that made some sense?
- Geoff