If you must reuse the case because you are a cheapskate, I suggest you buy your case fans, measure the required holes accordingly and use an angle grinder or related powertool to cut off the top side of your case for exhaust. Since you are using these kind of tools, might as well cut a significant portion of the side of the case to either mod in an acrylic glass for looks (you can cut along the bezel outline) or more holes to fix in more intake case fan (more practical/recommended). It wont be pretty, but you wont be a part of the overall ecological/garbage problem of the tech industry.
You can also try to remove the front cover and see what could be done in it. There is space for a front intake case fan. You could try to find out if you can mod another intake fan just below the optical disk drive.
Also RGB. Lots of RGB. To blind anyone looking to analyze the now moded exterior.
BTW the PSU looks standard. You could try to buy a modular PSU to reduce wires dangling about.