Hey I had the same problem
YouTube - To much power being sucked by car stero
I'am running a
2X JL AUDIO w7 13.5 inch
2X JL Mono 1000:1 Amp
0 Gauge
2X3 Farad Cap
I doubled up on the batterys earth
double earth the amps (didnt fix this problem)
I put an amp / volt metre on my car.... when the subs kicked it was Drawing so much power it was taking the voltage below 12 volts which means the car is giving up systems to keep everything going..
I kept losing "ABS and ESP"
(note dont let your car keep doing this as it is possible to damage both your car computers)
I bought a $900 Blue top battery 2500 CCA and replace the Front battery with a 670 CCA $350 (small truck battery)
this helped with the light dim but they still did alil on crazy songs and during comps!!!
Even if you install a 2nd battery its still possible to lower your cars voltage to below 12.5 volts
maybe try a cap.... try 2+ farad
you didnt go to insane with your stero but i did :$
i hope you just run 4 gauge from your block to amps.... if not replace the wire with some 0 gauge as i have seen 4 gauge glowing red when it is under to much draw and the guy was wondering why his auto vx use to stall.....