The Alternator is the part that will be your power limiter though. If you draw more than your alternator can provide, you'll kill batteries all the time, whether they are deep cycle or not. And by kill, I mean no longer functional, not just needing a recharge.
However, my guess is you'll be OK with the stock electrical. It sounds like if you want to run the system at shows though, you may benefit from a yellow-top (or similar) battery.