FUBU - it's all personal preference on how loud you play your music, the style of music, settings of your equalizer (if you have one) and if you've changed any components (head unit, amp, speakers). I would suggest you use some blade connectors on your car wiring and capacitor leads so you can swap capacitors until you find the right sound without having to cut wires.

As far as your volume coming from your iPhone, have you turned up the media volume on your phone? Just a thought.

RL