Mid range is where I would like to see the most improvement. At the moment my doors are not sealed and I think they actually do sound pretty good (don't know the exact model numbers off the top of my head however I'm running JL speakers and amps). I'm hoping that sealing the doors with MDF/perspex (still deciding which one to use) and Dynamat will increase the overall sound quality, however mid range is where I want the most improvements.

I would say my ears are quite good. Quite picky to be honest (most would say my system is quite good already).