Nope, all channels do NOT have to be used. If you do get another amp you can either:
1. just run the front components on channels 1 and 2
2. Bridge two sets of channels and double the power going to your front speakers (they can handle it)
3. Run channels 3 and 4 to your rear speakers (ew, you don't really want loud high frequencies coming from right behind your head)

You WILL NOT need another battery. You just need some distribution blocks (splits your wires up so you can hook up both amps).

DO NOT GET A CAPACITOR. They are less than useless.

When you install your amp maybe pick up one of these:

Its a power and ground distribution block in one. Used one in mine, then when I had 3 components stuck it in my friends car to install a second amp. I would just recommend a quality 4 gauge amp kit when you do the install and then you'll be all set.

 

they were recommending i get a battery if it is pushing to much power running through the system. i guess its one special one that will last over 5 years and is extra small at 80 that will supposedly never drag down my car battery. and yeah i will never boost the ones behind my head, i hate it now with them being 4 ohms and being louder than the door speakers(so i have the fad bumped to 3f) i will have to ask about the ground distribution block, this seems cheap but its another thing that i dont know how it works or what it is. also i do not have two amps hooked up until i decide to upgrade to a w6 or w7. ps just ordered my id's my setup should be installed w/in two weeks!i never thought i would end up spending so much, but i hope it sounds amazing

 

The most I've had is about 1300 watts RMS pulling on my Die Hard Platinum car battery, never had any issues. Right now running about 900 RMS with no issues, though I'm going to drop down to 500 soon as I simplify my system. You DO NOT need another battery.

The stinger block is just 2 Y adapters on a piece of plastic. It splits one cord into two for both ground and power to make it super easy to install a second amp. Some people will say "ITS GOTTA BE FUSED YO!" What those people don't realize is if you put the same sized wire on both sides it doesn't have to be fused. Just 4awg in and 4awg out and you're all set.

You can wait until you decide to install a second amp to install the distro block, means you can wait a bit before spending more money.

 

Sounds like a plan to me! i do remember him saying i dont need one right away and that if i started to notice dimming then i should think about it(battery) so i will tell them to go that route with the install since the extra battery could be added at any time. now im just hoping they can make a decent rack or something for my amps to sit behind the drivers seat, though i might put them in between the strut and front seats if they fit(update they don't fit) i cant find a rack either, if someone knows where to get one lmk! i saw someone on here selling them but it was from 2008 and you cant send pm's

 

If you order your box from Zenclosures, it will come with an amp rack. I will try to take pics of my set-up so you can see what I'm talking about.

 

i just got it today and it did not. and i didnt want one where you could see an amp

 

just an update i completed my install. i have:
-1 jl 10w1v2-4 sub in a zenclosure box
-one pac line output converter
-rear polk audio DXi650 co-axials
-front image dynamic ctx650cs with tweeters
-one jl 300/4 running bridged sub and front components
-behind drivers seat amp rack(cubby)
-a newer version of dynamat behind door speakers and under sub box

soon to come:

- bass control for just the sub
- possible upgrade/install of my 500/1 wired to a w3 or w7
- sts rear turbo mount :-) in maybe a year

i am still shocked how quiet my front speakers are for being hooked up to my amp... the sub is way louder and the speakers almost lack quality in sound as well. for near perfect reviews i must say i am disappointed in the quality. besides that install was cheap and what i did myself was fairly easy, and took less time compared to anything i did to the car.

 

Man really? I've been loving my Image Dynamics. I have a bit more juice flowing to them though. What did you do to set your gains for the front speakers? If you can, take a picture of your dial settings on the amp and post them up.