Aftermarket stereo headunit dims

[subru92svx]

I have a aftermarket stereo in my SVX which consists of alpine deck, front alpine component speakers, rear alpine 6x9's, alpine MRD-m1001 amplifier, custom box with two 12" alpine type R subwoofers, Rockford Fosgate 4 gauge amp kit, and 1 farad Rockford Fosgate digital capacitor. I also have a new alternator and a Optima red top battery. The problem that I'm having is when my subwoofers hit hard my alpine headunit dims a little. I bought the 1 farad Rockford Fosgate digital capacitior and installed it after being told by a few people that would fix my problem, but it still dims. I talked to a few stereo shops and after I told them I had already installed a capacitor they were kind of at a loss for what might be causing it. The only other thing I could think of was maybe running a thicker power wire to the deck it self. I was just curious if anyone on here might of had the same problem or have an idea how to fix it?