Maybe I'm misunderstanding but, if he sets the x-over for the LFE/Sub to 40 will he not only get everything 40 and below sent to the sub?

If that's the case, then he is missing too much low end and it will make his sub sound weak. My receiver only goes down to 80 for everything so for me to test this I have to use the x-over on the sub itself. If I set it to 40, very little BOOM comes out.

But, when I set it to 80, or to disabled by turning it all the way up, the BOOM is much greater.

"Tis better to desire that which you do not have, than to have that which you do not desire!"