@OP, the 805 matrix has a bit of a bump between 100 and 120Hz and falls off fairly rapidly below 80Hz so you probably want to cross it over somewhere around or below 80Hz. Ideally, use a set of bass test tones and an spl meter to check the frequency response of the speakers in your room first though, as the above is only a guide based on the room averaged response that Stereophile measured.
