Yeah, just the two. We do very very little floating with the stereo on and if it is on it's at like 5-10% (conversational levels), so haven't really seen the need for a huge stereo reserve. Mine's been rewired with a blue sea add a battery kit and the stereo is all on one battery, with rest of the boat on the other. Both batteries seem to be holding up similarly if my charger is to be believed (both will still hold a 12.5v charge a few weeks after being on the charger).
Nonetheless, when the time comes to replace, I'd sure like to put the biggest batteries that will fit.