my first big boy system

I have just ordered an 18" FI daily driver fully loaded. Its hungry appetite will be supplied by a Sundown Audio saz 2000d.
The box I havent decided on yet but the specs are somewhere between 5-10 cuft @ 32hz to be optimal for the daily use. It will be going in a 91 Silverado with no back seat. Im starting to get a look at more ways to build the box and speaker placement. Anybody have any experience with this kind of setup?
This project will be coming in the next few months and cant wait to hear it. It will have the big 3 and 0/1 ga wiring. Not sure if 2 runs will be needed though. Thinking of adding another batt and h/o alt to ensure good power. Do I need it? Also should I get like a 5 farad cap too? Ive always used them in all my other installs. Any advice or questions are appreciated.

Fi makes no "Daily Driver" line of subwoofers FYI.

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Custom Enclosure Design

Sorry about that. Forgot to put the type of sub...what an idiot. Its an FI BTL fully loaded w/ the daily driver opt instead of SPL.

forget the capacitor and invest in a good high output alternator and upgrade the big three with nice thick wire. you can get a 2nd battery if you want but one good battery will be enough if you dont plan on running the system too much without the engine running. you shouldn't need more than 1 run of 0 gauge wire for a 2000w amp especially in a truck because the runs should be short enough to not give you any voltage drop. where do you plan on mounting the amp?

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I wanted to mount the amp on a display board on top of the speaker box. Then I thought it would vibrate too much so I want to put it on the floor in front of the slot ports on the box.(if thats where the ports r to be)