I still haven't fully played with Linux on my rig. WIndows side I like Enterprise with Workstations as a runner-up. Server 2019 and lower are okay, they "feel stiff until you find the scripts to run against the REG files.
Hope you got your PSU replaced.
I have 4P 6386 SE and I have the system running at 216MHz. Maybe you've reached the upper limit of your CPU. As far as going to 220, I don't know if I want to push it that hard.
You should be able to troll eBay and upgrade your processors on the cheap.