head lights and cap

Hmm.  See, normally I might go along with this, except he's running a 440x2 ppi amplifier.  I'm not 100% sure but if I recall those are class A/B channels, regardless, you can guesstimate ~1000 - ~1200 watt pulls off his stock charging system.  So figure 80-amp spikes is on the conservative side of guesstimation here.  If you think a stock charging system could handle these pulls without symptoms, then you have serious misunderstandings about the amount of power he's using here.

I'm certainly not saying he needs a new alt.  There is a huge chasm between 'new alternator' and 'lights still dim after cap'

He's got a huge amplifier - not something that will totally overwhelm a charging system, but he's probably right about at the max of what a stock system can keep up with reasonably.  He's not experiencing dead batteries (presumably), but he's got some pesky voltage symptoms.  Reinforcing his engine wiring a deep cycle are the easiest ways to deal with this.  He does NOT need a new alternator.  That's a silly amount of money and time to throw at the problem.  His power needs just aren't that extreme. 

so to answer all questions. first i dont know what the big 3 is. 2 i am running a stock battery in a 08 carolla. i have the 400x running briged to a to w610s wired in series. umm yes but when i frist got the cap the prob went away for a bit but now its back. so if some one can explain it in the eaisies way for me to under stand that would be highly appreciated. i am a installer but ive only been in the game for 3 months today. i have alot to learn and all advice and opions are well taken.

Do the Big3 upgrade;

https://www.the12volt.com/installbay/forum_posts.asp~TID~73496~PN~1

Also, remove the capacitor. It's only hurting more.

Your car came with a 80 or 90amp alternator from the factory.