I have a fairly nice case and don't want to buy a new 1 at the moment. Its a mid-tower with 4 5 1/4" bays and probably 6 3.5" bays, so It has plenty of room.

It has 4 spots for 80mm intake fans, 1 side 80mm exhuast, and 1 rear 60mm exhaust.

Now these openings aren't the greatest especially in the front of the case. I am planning on cutting the little holes with wire cutters to open the whole openings. Think this is a good idea?

I also think I probably have too much intake coming into the case. Would a 120mm side fan really help expel a lot more heat? I was thinking I could buy 120mm fan and use my dremel tool to cut the opening for the fan. If you guys have any other advice on modding a "not so well designed case for cooling into a great one I'd love to hear about it, I tried the search but didn't really find much.

Thanks in advance

Yes, my case had slots for fans as well, but they were grated...lots of little holes...I took a dremel and cut the full circles out (2 in rear, 4 in front). I recommend it completely...a lot more airflow when it's one big hole instead of 30 tiny ones....

If your fingers are an issue, just get fan grills....

Go for it,,i did the same thing as schizoid77,To my RaidMax case,
My System temps dropped 6 degrees,and my CPU temp dropped as well.