Chevrolet Silverado electrical hookups

Hello, I have a 2002 Chevrolet Silverado and I wish to hook up three 12 volt accessories (amp, stereo etc), I cant see any free terminals on the fuse
panel in the cab. What options do I have in hooking up my accessories? I would like to have them switched so when the truck is off, so are the accessories. Also I cannot see anyway to run wires through the firewall...How does GM get the wires into the cab? All suggestions/opinions greatly appreciated.
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