Better late than never!!!!!!!!!!!!!!
Have been in Thailand for last month (holiday).:hurray:
Have you done your 8" in the back yet?
If not when you do them it would be good to cross the frequency going to the 8" speakers at a lower point the the 6" in the front. The 8" speaker will play better in the lower frequencies midbass(60-80Hz). The 6" speakers will only handle 80-120Hz. Because you only have 2x2ch amps, you would need to use both to do this(No subs)
There are formulars for working out wire gauge, simple rule is to use 4 gauge for both positive and negative to 2 amps. If you have 4 amps 2 x 4gauge cables or 0gauge. It all changes when competing but this is a good basic rule!!!
With the battery, you can add a second one in a number of ways. In parrallel(never disconnected will drian both batteries at the same time), through a switch(manual on/off if you forget will drain both), or through a solinoid(Automatic, charges and discharges automatically).
What model of rockford amps do you have?
When running two speakers of each channel of an amp, all you do is join the positives of the speakers together and the negative of the speakers together and use them as if it was one speaker. The amp will see a 2ohm load and with a good amp it will double its output.
Wire for the speakers i use 16gauge and for my subs i use 12gauge. But that also changes when competing. I have used 8gauge for subs lots of times.
I will hopefuly get my install done within the next month or two, but it is getting warmer here already, so might have to pospone because i want to take the doo for a thrash!!!!:hurray:
Hope this helps!!!