The flash is to turn on the fader and bass boom on the customs. Neather is needed.
How many speakers you running ? The ratings will be on the back of the speakers.
I just hooked up a Rockford Fosgate pbr 300x 2 with 2 Hog tunes 5x7 speakers rated at 50 rms 100 peak. I Set the amp's gain at 4 and it thumps those speakers.
2010 FLTRX , Stage 1, 13" Madstad, Mono tubes, SuperShox, Heritage style bars. Alpine CDE-HD149BT,Soundstream Picasso Nano Series PN4.520 , 5X7 and 6.5 Infinity Kappa speakers
If I have to explain ,you wouldn't under stand anyway.