there are a lot of car audio shops that can cater your needs for your car audio set-up. you may want to check the following shops: JC Car Audio, Mickey's Autosound, Blueprint, Sun-X, C&J Autosound, Autoline, etc.

if you have the budget then i suggest you change the stock speakers of your car. for SQ, you may choose the following seps: Focal, Helix, Brax Hertz, Micro Precision, etc.