Keep in mind Alpine's subwoofer controller is really an attenuator. At +15, it is at 0dB attenuation. At +14, It's at -1dB, and so on until you get to 0, which is -15dB.
It all depends on where you have the SUB-W control set when you set your gain on your subwoofer amplifier. If you have the Sub-W control set at 0 then set your gain, you will have major clipping issues if you run it at +15. OTOH, If you set your gain with the setting at +15, then running it at under +15 will obviously decrease the amount of bass you are getting.
I have a 9815 and I can drive my amplifier into clipping with the preouts on the head unit. This "Alpine has weak preouts" crap is just that, crap.
Someone didn't know how to set their head unit and gain settings properly, then it all of a sudden becomes a "problem" with every Alpine HU. //content.invisioncic.com/y282845/emoticons/rolleyes.gif.c1fef805e9d1464d377451cd5bc18bfb.gif