Do what I did... single 12" kicker L7.
Also, for those of you with a current setup, they do make dual 12 boxes specifically for mustangs.
2007 GT500 - White, Blue stripes, 2010 clutch, JLT123, SLP Loudmouth, VMP tune, AFCO heat exchanger, CHE upper/lower control arms, QA1 adjustable rear shocks. #360 of all GT500 coupes. 13,000 miles.
RWHP - ?? ~500
2012 Jeep Wrangler Sport 6spd - Daily Driver