I'll contribute a little........I have a DC 320 amp alt (150 @ idle) and was running a stetsom 7k2e to a 15" SMD sub in a Toyota Yaris. I have 300 amp fuses wherever they need to be and a STOCK battery. Big 3 in 1/0 w/ an extra 1/0 from alt. adjusting arm to batt neg. One run of 1/0 (+&-) to the Stetsom in the trunk & I was using jumper cable as speaker wire, haha. Now after getting the entire system o-scoped, the Stetsom was clamped @ a little over 3000 watts @ ~60 hz. With another run of 1/0 and two Kinetik 2000's I think I would have seen 4000+. As far as daily driving I push my equipment pretty hard. At idle I could drop all the way down to 10 volt if I wanted to w/ that amp but while driving and staying above 2000+ rpm............ voltage stayed pretty solid 14.0+ Sounds to me like you want to run 7k rms (as I had a 7k amp but only saw 3000 rms at best) so I'd say w/ a 320 amp DC alt and two XS 3100's you should be alright WHILE DRIVING. At idle, probly see voltage drop, who knows maybe not. 300 amps out to the batts should be over 3000 watts (if you get the 300+ amps) to the batts for charging. Now two d3100's as secondary batts should be able to supply power up to a 10,000 watt system iirc. All in all, I think you good, two more batts even better. Another alt your golden. Sorry for the "Novel" bro.