2000 Mercury Cougar really bad brake squeal/screech

I have a 2000 mercury cougar that I have just recently changed the pads and rotors on in the past five months. I put aftermarket cross-drilled and slotted rotors on it, along with some semi-metallic brakes I picked up from a local parts store. Since it's gotten warmer outside I have started riding with my windows down, and have noticed a horrible brake squea, which is actually more like a screechl. I mean. There is brake squeal, and then there is this. LOL. It almost sounds like metal on metal. I check all four pads and rotors, everything looks good. I put some brake disc quiet on the back side of the pads, and still I get the squeal. The noise sounds like it's definitely coming from the front brakes. I am convinced the noise is simply from when the pad hits the rotors, so my question is, could it more likely be the semi-metallic pad or the new rotors that is causing the awful screech when I apply the brakes? I was thinking about buying new ceramic pads for the front before I replace the rotors, to see if that works. What do you think? Have you guys ever heard of people getting this problem with either the semi-metallic pads or the cross-drilled/slotted rotors? I don't want to change out the rotors if I don't have to, because they were expensive and they look really cool, I am hoping it's those darn semi-metallic pads. Thanks.