Audio Systems: NO Sound, chrysler town and country, fuse boxes

Question
I have a 2001 Chrysler Town and Country with an after market Clarion AM/FM CD with AUX and a Sirius Radio. Everything has always been working. Then on Monday, I get ready to go to work and I have no sound coming out. I turn everything off and on. Unhook the battery for several hours. Even take it to a Car Stereo shop. They tested the Radio and it is fine, Speakers are fine.  They could not find the problem. (By the way they charged me 40 dollars) They said something about the infinity sound system and the amplifier or chip set.  Only the dealer can take care of this.   Is there anything else I could check before going to a dealer and getting charged an arm & leg?

Answer
yes there is  4 infinity amplifiers in the vehicle  but they all don't go bad at the same time  
on the right side of the radio there is a a relay,this relay turn on and off all the amplifiers
check the relay they go bad

also this relay needs to 2 powers one comes from the fuse box
the other power comes from the blue wire of the radio
check all the fuses on both of the fuse boxes
and check for power on the blue wire from the radio ,if there is no power there cut the blue wire from the radio and connect it to the red wire form the radio

i hope you use a credit card to pay the $40.00 call them they didn't solve the problem so they don't need to get pay