well,looks like i was wrong......the single black wire usually means non-amped stereo..... i doupt someone would mod a delco,but you never know......
try this,if the stereo comes on,then it has both power inputs (yellow on black plug is ignition) and orange on the two pin plug is memory/battery.
perhaps the protection circitry is on, meaning maybe you have a shorted speaker/speaker wire somewhere.
try this; turn off car unplug the front speakers (white plug) and turn on,see if rear speakers work, if so theres a short in the frount speakers and/or related wiring. if still no sound,turn off car again,reconect front speakers , disconect rear.try again......
another thought, is if you replace all four front speakers for the concert sound with aftermarket 4 ohm speaker and the way the factory wiring is,they will over load the radio's amp (the radio will see 2ohm

).
if this is the case, most likely radio output chip is fried. have it repaired/teasted or replace once you know for sure. if you have aftermarket speaker up front they need to be wired in series (8ohm) so the ohm load will be acceptable.