No. Just … No!
The CPU is more than enough.
You’re not sharing enough information.
The only reason why buying new hardware will improve your situation …
… is because you’ve reinstalled everything, changing the environment.
The issue will most likely come back to haunt you yet again,
because your hardware is not at fault.
First thing to test is your FPS when you turn off space graphics. That’s CTRL+SHIFT+F9 iirc.
If the FPS stays the same, we don’t need to look at graphics at all. Quick and simple.
You’ll have a grey background screen and notice the effect immediately.
It sounds like there’s something hogging your CPU …
… or that you’re massively thermally throttling.
Download this: HWMONITOR | Softwares | CPUID
Run it, run the game, take a screenshot of the thermals after waiting a few minutes and post it.
Repeat that for every scenario you’ve described.
Next to cover:
"Did this guy install pseudo-optimizer software?"
OP, in case you do have crap like this installed, which tells you that it improves performance … uninstall it. It does not. These programs usually lock other programs to specific cores, which is a really bad thing to do. So, again: If you use stuff like this: Uninstall immediately.
You’re not sharing the CPU graph of your task manager. Run the game in the different scenarios you’ve described, in windowed mode, have the task manager open in the performance tab. Make sure there’s a small graph for each core and then run “snipping tool” (hit WINDOWS-key, start typing “snipping tool”) to cut out a screenshot.
Are you running any AV? Deactivate it. It’s not necessary. They’re all more or less a scam. In Windows 10 you have the defender and the firewall integrated, which is all you need. Consumer AV companies prey on the lack of understanding of their customers. They have their software installed in bundles on OEM PCs because not doing so would teach many people that explicit AV software isn’t necessary anymore.
So in case you use one … remove it. It’s a ■■■■■■■ useless performance hog.
Okay, I want your input here before we move on.
The screenshot of the different CPU-graph-scenarios would be great.
A screenshot of your “AutoStart” in the task manager would be great.
A screenshot of your “Details”, sorted by “CPU-Time” (you need to add that one),
with highest on top.
Regarding upgrading your monitor:
That’s fine. Increasing the resolution will always affect your GPU performance, not your CPU performance. Unless it’s going to run at an higher refresh rate, there won’t be any difference for your CPU. Only if it has to push out more frames per second your CPU would be doing more work, but again … it’s not going to be too slow to handle it.