ok, first off, the big mistake you're making is seperate ground points. in a perfect world, or where you have enough wire & distances aren't too far, the ideal way to do ANY stereo system you want to keep noise out of is to ALWAYS ground EVERYTHING at the same point if at all possible. the reason you want to do this is, since your low level imputs on the amplifier are such minute voltages, any difference in ground potential between any two devices on the system get translated into motor noise (alternator and distributor) in proportion to the distance between ground points. also, the same thing applies on the other side..... i.e. when possible, connect all BATT constant hots to the same power connection - same reason behind it. doing just these two things eliminates 95% of the problems in installs (in the last 15 years, this is all i've had to do to eliminate any motor noise problems..... & i've done a lot of custom systems). maybe another 2% of it can be eliminated by running your RCA cables in a route that is as short as practical, but either at right angles to, or as far away from as possible in relation to your power cables. "filters" of the $10-$20 variety that consist of a small capacitor & maybe even a choke are a waste of your time & money, since the choke will only lower voltage to your system & thereby add distortion too). large caps are ok for getting rid of some of it, but by your description, i would unhook all those seperate grounds (god that was like the very opposite of what you should have done.... i can feel the other installers out there cringing at the thought) and find one very good point to ground them to. when you're done with all that, turn down the gains on your amps as far as possible. by that i mean the ideal setting on your gains should be where to hit your max volume, your stereos volume control would be set to about 3/4 of the way up. if turning your stereo volume up to only 1/3 or 1/2 the way up is blasting you out, you have your gains WAY too high- turn them down!