Over-Heating Issue

Better making a custom one

why dont you buy more fans to cool it down or check to see if you can underclock it

first of all what is overheating? gpu cpu?
run some stresstest on your componets and sametime look at temperatures.
if you didn't had that issue before then ur cooling paste is probably done u need to replace cooling paste on ur cpu and gpu
do u clean ur pc for dust? check those basic things out before u spend alot on watercooling systems.

Before buying a Water Cooling System try a high-end air cooler like Noctua NH-D14...it's cheaper, and it has a very impressive performance. That's assuming that your temperature problem is only in the CPU, otherwise consider changing your case (but first you should clean it, just in case dust is causing the problem)

Did you increased the Hz of your cores? If you have AMD - please turn it to the default value

Cooler Master Seidon 120V Rev.2