My apologies if this has been asked and answered elsewhere, but I had no luck in my searches.  Does anyone have a good answer as to whether a lightweight drycell battery is adequate for a modest car stereo?  I don't mean Miatabusa modest, but the standard 4 speakers and a 10 inch sub modest.  The lighter models from Braille run in the 10-20 amp/hours of reserve range and 200-550 cranking amps, but I can find no reliable references to the demands of a small amplifier (frankly, I don't have a very strong idea of what those numbers even mean).  I don't want to overtax a system and have evil electrical fairies eat my face nor do I want a dead battery when I listen to a couple of songs with the car off.  I know very little about electricity, so please keep the answers a bit simple.  Thanks in advance.