As title states need loudness and better quality of sound, starting a new build in my 2009 bmw x3 and for starters will be doing 100mm (4") doors speakers, tweeters, need recommendations on shallow mount 8" midbass woofers, and amp/amps for all of this. Once I finish with all of this I will start on substage and the basics will include AQ HDC4 18" with an AQ 3500D.1 most likely. So just need to make sure I will have a good clean sounding front stage which is why im starting this thread. Basically I will either be replacing the stock HU with a single din flip out, because a double din will not fit, or getting something like a cleansweep or EQ system tuning type device. I will appreciate the advice and product recommendations will also be a lot of help not looking to spend for than about $450 with shipping on either of these, please help! Will be ordering as soon as I get some help.