Capacitors
 

At which point do you need a capacitor and and do you selct one ?

NEVER! unless you absolutely want one, then you buy the prettiest :)

IMO i think they're a waste of $ and energy(literally)

You should spend your money on some 1/0 cabling and do the BIG 3 (<<---LINK In this post it was done on a caravan:smilie_da) before even thinking about a cap. Also, caravan need at least 17' of wiring to get from the batt to the back so use some good 4awg or 1/0 for the power.

I have both the big 3 and the cap but that is mainly because I didnt even know about the big 3 before I got the cap but I have zero problems with both...

anything over 1000rms you should consider at elast a 2+ farad cap and/or extra battery to support your electrical system

1 Farad = 1000watts

i dont believe the rule, but yes your right with that analogy. i'd just go with an extra battery, or an extra farad cap. it doesnt hurt to go a bit bigger, as long as you have a strong starter battery

going bigger in the capacitor area can harm your system. A bigger cap will need more power to stay topped up, which will steal power from the system because instead of going to the amps and speakers it will be going to the cap.

adding a capacitor to an already strained electrical system just add more stress...
the cap does not create energy
your money would be better spent on an extra battery,big 3 and/or a high output alternator

what the old guy said ^^^

settle down Grandpappi Yuli