Had a 6 speaker and 9 speaker.. in my vehicles before but I've gotto say that there isn't much difference if you spend your time chatting in your car.
But a world of difference when you crank the music up. The way i see it there's more difference between the 6 and 9 then the hifi model and HK.
This will be the first time i'm ordering HK .. during my test drive I wasn't sure if I was overwhelmed by the f30 as a whole that I thought it sounded better lol. Probably in my head.