Only a good quality woofer don't matter... list out your needs... what do you want out of sound... if you just want to add a little punch or you want everyone in your neighbourhood to listen...
I prefer a good punch that's confined within car... for that i'll go for a pioneer or sony xplode woofer with an amp plus the dimensions of box really matters... don't go for small box... go for full length box it will produce much better sound.