Thanks for the reply Luca.

I will be using the Dell T5500 case, and I'm not even confident that it doesn't use a proprietary power supply. I've only found one reference, on another site, that suggests it uses a standard ATX PSU.

I have looked for a bare T7500 case, but I haven't found any. What I already know is that the T5500 case is on the small side, and it offers a lot of opportunity for heat. So, I've already considered having to make some modifications to compensate for that, given that everything even fits.

Edit:

Though this is off subject, as far as I understand, only one CPU would ever be used while gaming. Even if a game used 12 cores (HT off), as I understand it, only one cpu would be used while the other one is ignored.

As a side note, this wasn't the original use of the machine. I wanted to give it to my friend so we could do some FPS gaming, but a different kind of GPU is needed along with a new PSU.

I have a Dell T5500 with dual X5690's and I'm wondering if a Seasonic 850 X-Series PS would be enough to power it along with a GTX 780 or 980.