ahooker

I've got a 92 sc300 and I put a 800watt amp powering a 400watt sub in it. Starting then I began experiencing power issues (fading lights, etc). I blew the sub and disconnected the amp, but the power issues are still there and now if I don't warm the car up like 5-10 mins minimum, there are power flucuations and sometimes the whole car just dies for a second. All the power just blinks off then comes back on. Is this an alternator problem or a battery or what?? Thanks for any help you can provide.