I'm just jumping in here..
But, did you mean to say your Subsonic filter is set at 50hz on your HU????????
I saw that, but that is prbably just for his doors. My speakers were toast if I didn't turn the SSF lowpass up on my HU because of all the boosted slowed music I played because they were on HU power. It didn't make my subwoofer any quieter either.
edit: wooops