Adding a amp and sub, do I need another battery?

[KillerMike]

I have a 97 SN obviously and right now there is a nice pioneer headunit thats in there now. I wanted to just ad a subwoofer and 600ish watt amp that I have kicking around, nothing too serious. Will I be fine the way it is like a normal car? Or do I need to add another battery? If thats the case then I will just leave the subwoofer out of the boat but if I can run it on the normal battery and be fine I will do it. Any advice would be helpfull. Thanks guys

[ski4evr]

I have three alpine amps and one battery runs them just fine, but I have another battery installed so when the brain isn't functioning properly and run the music too loud for too long while sitting, I can still start the boat. Paddling Sucks! Reserve power is very handy, used it more than once.

[RideButter]

Should be plenty of power there, but if you like to jam with the engine off, it would be nice to have a backup on a perko switch.