1) A blue top optima is for a boat. You're supposed to have a Red top or Yellow if you have 1000lbs of stereo equipment in the car. Go down to the marina and sell it then get the right battery for your application.

2) Check for sticking starter relay. The relays are mostly interchangable, so swap a different one into the starter position.

3) Check alternator ground and hot wire. The alternator cables have been a problem on a couple of my DSMs when they aren't tight enough, arc, and melt down.

4) As mentioned, check the starter but this is unlikely because you said no other lights come on, and no fuses are blowing.