I plan to buy a mazda 6 in a couple of weeks. My sound system made my lights in my grand am flicker like crazy. I had the stock alternator and a 3.0 bass cap. I plan to upgrade the stock alt when I get the mazda, but will this void the warranty? And what size alt should I get. My system is about 1300-2000 watts. Also, will most car audio shop do the big three upgrade and put in the new alt?