Volts times amps= power in watts....a KW is Kilowatt, just like a power rating for a electric iron or whatever in your house....1000 watts.....
same thing, but with a GREAT efficiency rating of say 70% for losses in the power amp....given off as HEAT, which is why those heat sinks are there....
the cooling fins....you get into consuming 1500 watts to generate 1000 into the speakers....well, if you do that we take 1500 and divide by lets say 13.5 volts as a decent level with engine running....giving us 111 amps under a best case scenario.....if you double that with two amps that's my rounded off 200 amps...
we ain't got alternators that can do that very long, not and run the car too....
getting into Leece Neville type territory, like a fire truck and a alt the size of a basketball or larger even....sometimes two of them....they have the room for that, a vette DONT.....
NOW, here is where it gets interesting....the kids drive these over rated amplifiers with going directly off the battery sometimes....and so they get a lot of 'punch' power, sometimes even using a HUGE size capacitor on the main power line,, the 12 volt feed....it's a help too....
so YES it is possible to generate a KW worth of power into the speakers for an instant, but that is into the woofers ONLY, second off, that instant is for about .1 second....100 milliseconds.......hardly a honest power rating for any amp....steady on for ten minits is a more honest rating....when trying THAT, those amps will blow up......literally, smoke, fire, heat, whole thing...:gurney::evil:
No sense in getting all techy on you.....but I"m a olde tyme elect tech from WAY back, with an equally olde tyme stereo hobby, mostly home systems...
Decades ago I had a friend with another '60 vette, much like mine....he put a very nice stereo in it, with custom dash and 8 track player system, before any factory ever heard of it....made from old 'spot pack' systems the disc jockeys used in radio stations for playing commercials...known in the trade as 'spots'....