At the amp swap the left rear for the right rear. If the noise stays in the right rear speaker then it is the wire or the speaker. If it moves then it is the amp or before the amp.

If it moves, put the speaker wires back proper and swap just the RCAs going into the rear left and right. Now is the noise in the same speaker or did it move. If it is in the same speaker, it is the amp. If it moves it is before the amp.

Continue this way until you find the point where it stops moving. This is where the problem is.

Troubleshooting like this is tedious but you will find the offending piece.

 

I made a picture. Hopefully it's clearer then my words.

EDIT:
I'll try that when I get home. Luckily I have a small 4x6 kicking around to help test. Thanks for the method. I'll let you know what I find.

 

Like Dukk said
Use a process of elimination to find the source of the problem. switch amps, speakers to see if noise has changed location.

 

Well I fixed it... after 3 hours. The solution doesn't really make sense to me either.

The guy who installed my mono amp didn't sand off the paint where he grounded it. But when I installed the 4ch amp I did.

So when I noticed this, I grounded off the paint where the mono was grounded and re attached the wire. After that the clicking of the 4ch was gone.

Problem solved. ^^

 

hmm MTX amps are really nice cause they have the auto turn on, i think you would have a bit more sound quality if you split before your clarion amp because your using your sub amp as a spliter and theres lots of electrical junk going on in there, how nice are your rca's and the best sound quality comes from a straight input from the deck so if you could pick up a good deck with three outputs life would be good?

 

nvm good job fixin her up (y)