battery relocation

i'm contemplating this mod... i know i need to upgrade to a sealed battery and that i need to secure that beast so it does'nt fly through my windshield. however, i was wondering will my existing 4 gauge suffice or should i upgrade? And i know one of the functions of the (high quality) battery is to back-up the diodes in the alternator and reduce a/c ripples. will having my battery in the trunk reduce its ability to "filter" my power?