With PSUs, there is either not enough power or enough power. There really isn't much of a middle ground that is going to give you better fps, etc.
If you have an underpowered PSU, it will cause things like random reboots.
With a system like yours, you may want to consider getting a more powerful PSU. It also seems like you are using a PSU that came with your case. These PSUs are fine, except they usually don't supply as much current reliably as a brand-name would
Have a look at this power supply calculator
and see if what you have is enough. I usually give a little leeway when deciding on a PSU. If I am using the one that came with the case, I'll go at least 100W more than the calculator says. If I go brand name, I'll go 50W or more than that calculator says.