multiple battery, the best way

New guy here...

I want to be sure before I hook up my newest system. Untill now I've had 4 pro-tec 15's w/ 1 100HC by audio art. Now I have 4 13w7's with 2 100HC's. These aren't hooked up yet.  I am not opposed to buying new amps but I am more concerned with the power supply.  I have a 2003 silverado ext cab. I plan for extra batterys, but how many? (2-3)  Does the ground on the batts go to the frame or back up to the engine compartment?  I have a high-output alt and have done the engine compartment upgrades.  Is there any point in a cap/hy-brid cap in addition to extra batteries? I enjoy looking through the previous postings there is always something new to apply. Thanks for any tips.

Ryan 

Aruman makes a good point about the alternator;  that's where the power comes from.  Figure up the power draw of your sound system and the capability of your present alt, with the thought that the truck's accessories will be using the lion's share of the alternators power supply.  Also, if you haven't yet, read the featured topic "How to upgrade the Big Three".  oops...I see in what you wrote that you took care of those already!  Good!

Other than that, here's a diagram I made for another poster who was putting in a 2nd battery/cap hybrid near the amplifiers, from this thread:

In his case, he reported that the batt/cap instructions said to wire both the pos and neg in parallel with the main battery.  So in this case, all the components are grounded directly to the batt/cap.  The main points I'm making with this diagram is the subject of fusing:  that every additional battery is a high amperage power reserve and needs fuses on each positive power wire that is routed from it.  And, that smaller power wires that are split off the main wire need fuses, too.