I know that those 6x9's don't extend low but they BUMP HARD.
Moreover... I feel that a lot of people actually prefer the kick and feel of midbass more than the rumbly earthquake?
The First video sounds insane!! I can feel that bass deep inside me... and it sounds like it can get pretty low too! (I have a nice 5.1 home theater hooked up to my comp so I can hear the sound pretty well). 2nd video sounds like sh1t... but wtv.
Personally I don't really like my JL 12W6V2 just cause it can't kick mid notes (80-120Hz) nearly as hard as the "pos" factory harman kardon 6x9's when the bass eq on my factory deck was maxed out. (I have a 2003 BMW M3 too)
It does a great job being a "sub" but I dunno... I feel my music just isn't as rich anymore (I can't feel it nor really hear the low end midbass). I'm running K2P's in the front too crossed at 75Hz @ 12dB. I'm downsizing to a 10" to see how it sounds.