Some news:
Dad says he has a 500 GB hard drive, plus I currently have two old WD Caviar 80 GB HDDs right now, so I can easily do with 760 GB for now.
I am literally using my phone's flashlight to look inside while typing this on it so yeah, hopefully I can get fully detailed specs of what I have now. Also, CPU cooling doesn't seem to be an issue because I have plenty of that (if the new CPU comes with fan and heatsinks that will make three for me, plus a huge fan on the case) this case was built with CPU cooling in mind so yeah. And if you were wondering the exact amount of hard drives I can fit, I am looking at a total of around 8