Have we considered temperature issues?
Yes we have. And temps don't affect performance on a desktop except when they reach throttling values which are generally above 100 degrees Celcius; the only thing they might do is reduce the life of a component, not cause low fps in games on a new rig.
If you know everything already.... why are developing an attitude to people trying to help you here? Sure, you seem intelligent and like we could get along, but why would someone help you if you call people's simple advice "trash".
Just yesterday, someone built an amazing pc with decent onboard graphics. Their games ran fine if they were older, but newer games ran at ~15 fps on low. We narrowed it down to a simple mistake. They plugged the DVI cable into his onboard adapter.
Now, onto what is going on... No, even the games you are listing should not require that kind of processing power. In today's gaming world, an i5 2500 (k or not) will not be the bottleneck. There is a lot to look into. What kind of software do you have running in the background? Have you tried running a program such as GameBooster, or manually killed processes and services that are not necessary to see if any are causing a spike?
Have you ensured that any specific BIOS settings pertaining to your processor's speeds are set appropriately? I do not know your BIOS nor have I used a 2500 personally so I cannot know what is in there...
I disagree especially since if you GPU is over heating you will get frame drops, this happened to my friends recent build(granted a faulty AMD card), the GPU was faulty and overheating causing slow frame rates crashes and poor performance, all of the things you seem to be describing to us, so you need to look at either what is happening software wise on your system or consider that the problem is not your CPU but maybe your graphics card.
(on a side note but very important, learn some manners we are doing you a favour by helping you, we are not getting paid to sort out your issue so so start with the basics, please and thank you go a long way!!)
What anti-virus are you using, and have you tried turning it off while playing a game to see if it makes a difference?
Eset Smart Security. And I just tried, turning it off has no effect.
Well if you really want the answer (which is irrelevant in this case), yes.
But do you need a faster CPU? No.
Good luck with figuring out what your problem is.
Here's your 3dmark score for an i5 2500:
If I recall correctly yours was even highe than that so I think the CPU is performing fine.
If you have done the clean install of the OS and drivers and everything is plugged in correctly I can't think of what the problem may be. It doesn't sound like a hardware issue to me but to be certain you an try swapping the video card out with a spare or borrowed one.
Daaaamn it's actually higher lol. I guess it must be a software issue, I'll format again, but this time I'll install windows 7 Home Premium instead of Ultimate instead and see if it's better. But why is my GPU score 6378 lower than this http://community.futuremark.com/hardware/gpu/NVIDIA+GeForce+GTX+580/review#? My card is a factory overclocked ASUS GTX 580 so it should get a better score than the Nvidia GTX 580 shouldn't it?
Eh, there close enough (2% difference) I would guess its just a difference in the systems and wouldn't be a notable difference.
First of all: set performance mode on windows control panel (inside power management)
then on bios disable c3 and c6 steppings, spread spectrum, virtualization and set as main gpu your pciex, totally disable your IGP (your mobo does not have a graphics card, but your CPU does have an IGP, you must disable). ALSO, uninstall Lucidvirtu if you have it installed and intel graphics accelerator or go to harware manager and disable HD2000/HD3000 video processors.
thats about it. if that doesn't help, then there's a hardware issue