I'm more of a punchy 6x9s man as long as they have a good amp - otherwise anything driven off the head unit sounds so crappy once you're used to a decent amp.
I used to have a 12" sub, always got annoyed with it moving around and having to remove and add it everytime.
6x9s are nice and light, can still sound decent if they are in a solid wooden mounting base thing with some good 3d volume like a sub box and driven by a decent amp.
I'm gunna get a new head unit soon and do something pretty custom in the back (now that I don't have any back seats) to mount some 6x9s and an amp. Kind of side mount them to an angle etc. Need to hook up some custom MDF things to mount them on yet.