CPU upgrade - advice?

My specs:
Lenovo H30-50
Intel i5 4460k 3.2 GHz /1600/4C/6M
Cubase 10.5.20
Windows 10
Audient iD14 USB audio interface

I want to upgrade the CPU for better performance, and need to check on the forum for advice.

Some of my VST instruments (especially synth pads, in Halion SE and Padshop 2) push the performance meter into the red and sometimes cause digital distortion. Increasing the buffer size gives me more ‘headroom’ of course, but I would like a more powerful processor. (Side note: 16 GB RAM is the max for my machine.)

Apparently, my computer CPU can be upgraded to an Intel i7 4790k 3.6 GHz /1600/4C/8M

What I want to know:
Is a CPU upgrade worth the price (probably around US $250 used and $400 new)?
Could I get significant performance improvement?
The computer cost me around US $850 new many years ago. Maybe I should just get a new computer?

BTW, while running Cubase, my Windows performance meters show a steady 50-55% usage of RAM, and CPU usage fluctuates between 30% and 60% (or more).

Thanks much in advance!

Well, it’s not worth it, $400 for such an old CPU is too much.
Better save up for a new motherboard, CPU and DDR4 RAM.