batterys

I have a 1997 Toyota t100 xtra cab 3.4l v6. i have a thiram's 3k a and a CT sounds 400w 4 channel amp with a big 3. I'm running a avatar stu-15 3000w rms 6000w max. I have a 2nd battery which is the XS Power D375 XS Series 12V 800 Amp AGM battery. am getting ready to upgrade to a 240 amp alt and...