Zumbo,
the best way - IMO - for setting up the LFE channel is to leave the LFE channel level on AVR @ 0dB, even though Audyssey says otherwise.
The reason is to avoid the output stage in the AVR to overload the SW input stage, + to maintain the noise level below audible level.
Then comes the XO setting, which I leave @ 120Hz on AVR, so in case I want more (or less ) bass, all I gotta do is to adjust the volume knob in the SW properly. All my speakers are crossed @ 80Hz though.
My speaker setup comprises:
03 X SVS SCS-01
04 X SVS SBS-01
01 X SVS PB-10 ISD.
As I said before... no complaints at all