quick question, i usually listen to my sound system with my car off. Would there be any complications to listening to it and charging the battery at the same time
A charger doesn't proveide that much amperage, and by having your radio on while charging will deprive your battery from charging quicker because all the juice from the charger would go to you radio and acceccories
^ but your alt still is able to produce much more amperage then a charger even at idle. In fact, using a charger while listening to your system could possibly discharge your battery, just not as much as no charger. Usually most car chargers provide 10 amps as a fast charge. It doesnt take much volume to use up 10 amps. If you go over the charge rate, you will be using battery power anyways.
If you would want to keep juice pumpin without affecting your battery with your car off, look into a high current 12v power supply.