Ok so here is my current setup. I currently have an Alpine 4 Channel amp powering up all my four speakers and a sub (I know it's not optimal, but I had a car audio store hook it up like that). At first I had a used Sony Xplod amp. After listening to music for about 15/20 minutes while driving, my front speakers would start to make a continuous crackling sound with a 10/15 second interval. They would also make this sound when I would put my foot on the brake. I had someone diagnose my system and he told me it was the Sony amp, and that they are known for this. So I replaced the Sony with an Alpine MRP-f300. In fact I did this today. But after listening to music at a moderate volume for like 7 minutes, I noticed that the brake problem had persisted. I'm pretty sure that they would also make the crackling sound by themselves like they were doing with the Sony, if I listen long enough. I could be wrong though. Now my question could this problem be due to having a 4 channel power 4 speakers and a sub? I heard from someone that that could cause some problems, and he mentioned crackling. So is it most likely the 4 channel amp setup? If not, what could it be? I'm going to the store tomorrow again to have them take a look. Should I change the setup to have the amp power my front two speakers and my sub? Is that what you guys would do? Any help is appreciated. Thank You.