[carmadbaker]

Deffinately amp the speakers up mate, i found regardless of quality of the H.U they distort at high volume level. Generally have poor control of the output and sound fairly crumby to be honest.
As for the lights dimming....i've heard a few different solutions, and found they all work differently, best option i found....turn the subwoofer down, reduce the gain. i personally whacked a power cap on my old 200 and hey presto the problem stopped. don't get drawn into the old "the greater the farad capacity the better" rubbish though, any rating will do. i won't be a geek and explain, but a 1 farad is just as capable as a 2.5 farad.
My zed only tends to dim the internal lights (because i have seperately powered HID's) when im stationary and really pumping the tunes.