It is not only possible, but is quite a common practice to do so. The only thing you have to remember is the amp rating on the wire you are using. For example... if the wire is rated at 100 amps, you need to make sure you don't have enough of a draw from the amplifiers to max this. otherwise the wire will catch on fire.Question:
Is is possible to run one wire from battery to trunk, where amps will be located, and have a power block back there to run power to each amp? This would save a buncha wire running the entire length of the car for powering each amp (there will likely be 3 amplifiers).
Thanks for your help.
Also, can someone tell me the best use of an Audio Control electronic crossover? Which model works best for a four-six speaker + one sub woofer system (multiple amps)?
Use a circuit breaker up front. Make sure it is rated for more than your amps will produce, but don't overshoot too much. For example, if the amplifiers will draw 100 amps combined, use a 150 amp breaker. Use individual breakers for each amp in the back, too. Follow the same rule. If your amp draws less than 80 amps, I would probably stick to a 100amp breaker.
Your safest bet would be to add a battery in the back. When you stretch power wire out for great distances, the resistance on the wire will usually do a decent job at hindering the ability for the wire to carry constant power. If you go this route, make sure you have a breaker after your front battery and another in front of your rear battery. (Both breakers on the wire between the batteries.) You definitely don't want your car catching on fire. If you do this, usually the internal fuses on the amps will be good enough for the 1' to 1.5' worth of run from your rear battery to the amplifiers. Its safer to put fuses or breakers inline with that power wire as well, but its not required. I almost never bother.
You will notice I am putting a considerable bit of emphasis on breakers over the use of fuses. There are two big reasons for this. First is cost. In relation to fuse blocks and fuses, they are cheaper. Second is the added benefits of being able to manually control the power from one source to another with the flip of a small lever. Not to mention the fact that if you ever get a power surge, you won't have to go scrambling for more fuses at your local store. They can be had for anywhere from $15 to $30 for a descent 150-200 amp breaker. You cant touch blade fuses and holders for that cost.
As for the crossover... if your amps and headunit are worth anything at all, they will have ample ability to tune your system. The use of an external control shouldn't be needed. If you still feel the need, though, you will never hear me recommend an AC crossover. They are, in my experience (5 times over), complete junk.
No need to post on any other forums... I got you covered. But if you feel the need for a second opinion, I recommend Car Audio Forum. They will only repeat what I have already said, though.
I try to be here as much as I can, so feel free to post any additional questions and I will try to answer them.