You should try photobucket or another host for your pictures.
Anyways, I highly doubt you fried your RCA's. Your head unit doesn't throw enough through those wires for anything to be "burnt"...ever. Even if there was a macrocosm of events that shot a spike through the RCA's, it still wouldn't be enough to "fry" them. That's because the total power that your head unit draws isn't enough to damage an amplifier or even the cables through the length of your vehicle.
Sounds like your amp is damaged and whenever that cap or whatever it was went, it through a surge. Electricity is ALWAYS looking for a place to go. When your ground is overwhelmed those surges go wherever there's a wire willing. Apparently, that surge reached out to your RCA's too. Good thing the components leading out to your RCA's can't take that much abuse or else you'd probably be replacing a head unit as well.
It honestly sounds like you had a bad setup. That doesn't necessarily mean that all your wiring was bad or the amp is a piece. It means that tuning, install, and proper setup should all be questioned at this point.
Before you throw something else in I'd make certain that you install correctly. That means verifying your entire thought process with an experienced individual prior to throwing that volume knob. Just because it does fine at low listening levels doesn't mean it's operating correctly either.
I'll help if you want but I would request that you provide photos of the install and even pictures of the crossovers as well as gains. I'd also need all technical information for the equipment being used.
