Well RFoster I put in a second Optima Blue battery in the same location you put your second batt. I went ahead and tried the battery combiner which I kinda regret because I had to rewire my stereo and all accessory power wires over to the left side of the boat so that they could power from the second battery. Basically the combiner seperates the two batts when voltage from the alternator, or house charger is not available or the common voltage is below 13.4, or 13.3 i believe. I got my depth sounder put in as well along with two more Polk Tweeters. All in all I have been working about three-four hours a day for the past week doing all this... The Perko Switch would have been the way to go labor wise..whew...Oh I had a 5.25 Polk go out as I mentioned before, so I'm trying to see if anyone has just one available on different audio forums.. I kinda got the ind knocked out of my sails on the subs when I saw that they had gone up from 50 shipped last year to 80 now for the same thing..For some reason Crutchfield Audio list regular Kicker Comps as marine certified if you look on their website, but I'm thinking that may be a typo on their end...???.. May just wait until you upgrade if you decide to, and get your hand me down subs:cheers: