Get a bigger or "faster" battery. AGM batteries like kinetik are designed for audio systems. You could always get a bigger alternator too. You can probably get away with just some big deep-cycle battery though (I do just fine with a sears die-hard battery for audio).
It may not be a problem that the voltage is dropping like this though. 10.5 isn't THAT bad. Though 10.5 is considered a flat-dead battery. Check your batterie's voltage with nothing on. Try charging it to full capacity before doing anything and see what happens.