I totally agree with your recommendations. I did bring it down to 30 HZ but not to 25 HZ and the reasons are as follows,
I have a Home theater 7.1 system which is as follows
B & W 802D Front Speakers
Frequency range -6dB at 27Hz and 33kHz
Frequency response 34Hz 28kHz ±3dB on reference axis
B & W HTM2 D
Frequency range -6dB at 35Hz and 33kHz
Frequency response 41Hz - 28kHz ±3dB on reference axis
Monitor Audio PMC 702 Reference
Frequency response 35HZ - 20KHz
Frequency Response (Hz, +/-3dB) 110 Hz - 20 kHz (+/- 3dB)
Now on my processor, I cannot lower down crossover frequency below 40Hz.
Just clarify, front speakers are set to full range for base and not "Full + Sub". I have a separate connection from processor to .1/LFE input.
Now front speakers have a frequency response from 34 Hz and up and that's why I set it to 35 HZ.
My questions are
1) If I set my sub-woofer to 25 HZ, than what happens to frequency from 25HZ to 35Hz which cannot be played by these speakers.
2) Several people commented that by adding this sub-woofer they got a wider sound stage. If I drop the crossover frequency to 25 HZ, how someone can have a wider sound stage, I am not very knowledgeable in this field but I think when someone says wider sound stage that means some of the mid-range frequencies are played through the sub-woofer. But will they at 25db?
3) For surround sound (7.1), if my processor has a lowest crossover frequency response of 40HZ and I set my sub-woofer to anywhere below 40Hz, what happens to the difference?
All these questions are because I paid $4500 for the sub and another $2500 for two cables one High level input and one for .1/LFE, so I want to do it right and I don't know what is and who to make it right.