i was once running 4 bxi2607ds off 2 powermasters. i had a stock alt, but a very good one for being stock. and over 200' of 0 gauge. didnt work for daily. the hdc3s are only loud with more power. running only 2 batteries the sd2.5 series will be better. i found the hdc3s to be way less efficient than even my type r's under 1500 watts. ie) my type R's could bassrace a 150 easily, and the hdc3s couldnt.
your truck would be perfect to put a d3100 in front and fit as many batteries as possible into that tire well.
idk what murphey is doing. i am sure when spring comes he will do something new because even last year he wanted something louder.