I had a system in my 68 stang and it had a crappy battery, well I was on a mustang cruise battery died and the cruise was to a performance autoparts store and he sold me a new redtop for 100 bucks. afterwards dimming was little to none where as before it was terrible, yes it would be an upgrade for a stocker like mine but there are better. I love mine its been through 4 of my cars, dropped fell out of the battery tray, into the fan and then through my timing belt cover, still is fine to this day.
it would be fine for stereo as long as this is all you can afford. It is better than stock but please remember that there are far better batteries out there for car audio. but the red top is a great started battery.