Great work!!! I've got an '18 SL that I'm in the process of updating the stereo in as well. I've got a 1/0 power wire from the battery to the distribution block, feeding to PG amps with around 3k RMS. You'll be fine with all of the plans you have. I would recommend keeping it simple, at least initially until you find the weak points. My setup draws about 60 amps of current (for a brief moment) but normally runs at around 15-18 amps during normal listening.