How to Adjust Equalizers

[TheTallMan]

Just curious, what is the best way to tune the audio in my 2004 X5?
I added a sub to my stock DSP system, it sounds pretty good, although I need to lower all the bass since the system can be overpowering. I have a lot of places where I can adjust the frequency content of the music,

- my MP3 player has an equalizer (I have an AUX input for it)
- the head unit has a DSP equalizer
- the head unit has bass/treble controls
- the amp for the sub has an adjustable crossover/low pass filter

Is there an order in which I *should* adjust these to get the best sound, or is it just "make it sound good" approach? I get a lot more bass when my input is FM radio, vs if it is tape, Sirius, or Aux input.

Also- what is the "room" setting on the DSP system for, it seems to be coupled with the "echo" setting (whose function is clear); did not see much about in the radio part of the manual.

Thanks-