I wanted to get a decent 4.3-4.5 ghz OC at least on my 4670k. Will it be possible to do that with this case? Will any of the monster heat sinks fit, maybe with the side panel off? The PSU sits at the top, above the cpu, and there's no way I can mount a radiator, so h100i is out of the question, unless I buy a new case, which I may need to if there's no other choice. Are the big heatsink towers like Noctua & Silverarrow unable to do the job properly in a case like mine even with the side panel off? If I must get a new case, what has nice cooling and is the biggest bang for my buck? I just want to get a nice stable OC at 4.3-4.5 ghz with either a mega hsf or closed loop cooling, but I'm at a lost as to what would be my best course of action. I would much appreciate any advice.
There's a good article on the front page of Tom's Hardware reviewing some low budget cases.
That being said, your case should work fine. Just check out the exact dimensions you have available to you. Measure around where your current CPU sits, then compare that to the sizes listed on any cooler you're looking at. There are plenty of nice coolers that don't look like monsters. Sure, you won't get the best OC potential, but it sounds like you're just looking for some free bonus performance out of the OC.
I'd generally recommend stepping up to a case that uses at least 120mm fans, just to get some help with airflow. Not sure what GPU you're going to go with, but you have to consider airflow to that component, as well as where it is exhausting its (very) hot air.
Check out the reviews on Tom's Hardware of the "Sub $100 Cases for Your Gaming Build". $100 on a case goes a long way these days!