Tuning help

Hey.

Just need some help on the subsonic filter business and lpf.  As its giving me a headache. 

I have a Rockford Fosgate P3D2 in their own ported box tuned at 40hz. Its a 600rms sub. 

Im running it off a 650rms amp. 

On the amp my options are gain, bass boost, subsonic and lpf. 

Subsonic filter runs: 15-35hz

Lpf: 30-250hz

Now the bits i need help with are the subsonic filter and lpf. 

Any reccomendations what to set these too? 

Thanks