Well, it's been a fun run for my HP 8300 Elite CMT. I just sold it off and went for a i5-8400 custom build. Not that the performance was bad (it was actually spectacular), but I just had too many issues with it—random reboots/black screen after sleep with Nvidia and system wide lock ups with AMD. Tried for months every kind of configuration, kexts, changed RAM + CPU and issues still persists. Tried multiple Nvidia and AMD cards too. The freezing with AMD I believe has something to do with not enabling iGPU on the BIOS, but the HP BIOS doesn't have an option to enable such feature. Even tried to run it off just Intel HD4000 graphics but my 4K monitor just didn't output anything with the DisplayPort. I just got fed up with troubleshooting it more than actually using it.
I also dislike HP and their proprietary shenanigans. Why must the power supply and motherboard connectors all be proprietary? Even Dell Optiplexes use standard ATX power supplies and connectors. It renders GPU upgrade paths limited since you're stuck with lower power variants that doesn't require 6 or 8 pin connectors.
Anyway, that's my rant for today. Hope everyone else had better luck with theirs. I just couldn't get mine to be stable and my hardware is vanilla as possible, unfortunately.