try checkin your rcas from the back of the radio as well. one of my rcas came off for my subs and for the longest time i couldnt figure out what it was until i pulled out the deck and saw a rca was unplugged.

ps. check your grounds, the rcas running over the power wire may also be a factor but it is not always true. my boy has got his rcas ran over with power wire and he gets no noise. i had mine ran the same way and no problems. u also might have bad rcas