I have 2 amps running maybe 1600 max power and 800 RMS and I haven't had a problem yet. Just make sure that you turn your radio, and really all other accessories, off before you try and change tunes. You will always have battery draw with the truck off, and with the truck in the on position, but without the engine running, you will have quite a bit more even without the stereo system running.
If your truck sits a lot I would get a battery tender like Jack said, that should keep the battery up even with the system (when off it shouldnt draw any extra power than just the radio).
Hope that clears more up, and feel free to keep the questions coming!
