Adding more memory has no effect unless you are maxing out memory, check task manager.
A bigger power supply would only be necessary should you switch to a new power hungry video card.
Swapping to a faster disk or a SSD would improve performance, but the biggest improvement with a SSD drive would be in boot time and processing of very large files.
Help, my PC with Windows 10 won't shut down properly
Since upgrading to Windows 10 my computer won't shut down properly. I use the menu button shutdown and the screen goes blank, but the system does not fully shut down. The only way to get it to shut down is to hold the physical power button down till it shuts down. Any suggestions?