Benchmark Stress-Test Config

[Boobus]

"So you've just assembled some components together and gotten everything up and running. Before finalizing everything with establishing the O.S. of choice and then utilizing the build for its intents and purposes, where do you go from there?"

Myself, I have had two computers that I initially built almost(*) ten years ago now. They still work quite well, especially considering their age. Now that they are almost as old as they are, I feel simply "upgrading components" wouldn't necessarily cut it. It's time to tinker with the digital aspect of them ... in other words, Over-Clock.

It's not enough though to just be able to go into the BIOS and tweak some values here and there, I need to confirm not only that there's improvement, but also that there's stability. After all, I wouldn't want to take these beasts out of their prime just because I accidentally increase some voltage-outputs to a degree that "Fries the system."

What sort of applications / software's should I be looking into to provide feedback on stability and stress-tests, or even the possibility of dummy-o.c. (outside of BIOS)?
*RAM / GPU / CPU / ... I'm too new to these things...*

 

[Boobus]

The Rig's I'm working with, that I would like to overhaul to last for a few more years--if possible--are:
ASUS Rampage Extreme x48 Motherboard with Intel's Qx9770 CPU
&
EVGA 790i Ultra (132-CK-NF79-A1) also pair'd with Intel's Qx9770 CPU

The two builds are fairly identical, other than the motherboards themselves.
Both are running with 8GB of Corsairs Vengeance 2000MHz RAM and EVGA's GTX 460's, with a 256GB SSD C:\ (and additional RAID 10 secondary storage) all on a 600W PSU.
I've been considering upgrading the video-cards to something that will undoubtedly support DX12 and ensure these' rigs' longevity into the future, but I don't know what a viable replacement video card would be for these builds -- or, if I could even use a third party software to manually tweak the GPU configurations, well.

Everything is assembled and configured in it's optimal-default settings. I have not gone into the BIOS and adjusted anything, since initially building them.

I think that I can get a guaranteed improvement with their performance by adjusting some settings in the BIOS. But, what do I do to "test" them and ensure Stability / etc.?