If you can make some money by selling a nice sounding 4" component set -E90 and F30 Sedan and Coupe fitment, meaning 40mm or less, with the matching OEM 3-hole mounting frame- for less than $200 then this will be a great effort.
Otherwise, good luck fighting your way into a well established and great sounding 4" component market.
-2015 F30 320i, Imperial/Oyster, 8AT: August 2014 ED
-2012 E92 M3 Jerez Black/Rust Brown, M-DCT: September 2011 ED
-2008 E90 M3 Melbourne Red/Bamboo, 6MT: Gone
-2007 MK5 GTI United Grey/Grey, DSG: Gone
-2004 E46 M3 Carbon Black/Cinnamon, 6MT: Gone