First, I don't think there are any cons to a dual battery setup. My boat didn't come with one from the factory, so I added one. I went with option 3 (the blue sea add-a-battery system). I think it is great. I have one marine starting battery powering all the engine stuff, and I have a second marine deep cycle "house" battery to run just the stereo. This system also does not need to be switched back and forth, you just turn it to on and go. The relay handles the load distribution and the charging. So i just turn it on and forget it too. I use turnthe switch off every time we get done using the boat just as a precaution I guess. I am also sure that the stereo is totally off and not drawing juice while the boat is sitting. The only bummer is the memory, but I just need to swap the memory power wire and run it straight to the battery.