You should be fine with 4 gauge to the back. But that 0 gauge will help voltage at the amps. I would only do the big 3 in 0 gauge. Most factory wiring is already 4 gauge.
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MECP Certified.
Alarm: Viper 5200
HU: Stock
Active Set-Up
Tweets: Image Dyamics CD1pro mini horns
Mids: Sundown Neo Pro 8s
Amp: Kicker IX500.4 (2)
Sub Stage
Subs: (2) Dayton Audio 15" HF
Amp: Kicker IX1000.1