Go to the SVS website.
Scroll to the bottom of the page and in the middle, you will see a link labeled "Merlin".
Merlin - SVS
Ostensibly, it is a tool for selecting an SVS sub to match your speakers, but it is also an adviser for sub settings.
Not using the bass management of the AVR equates to what they label "2 Channel Application"
I don't know which speakers you plan to do this with, but for Home Theater Direct, Level 3 Bookshelf Speakers, they recommend:
Set the sub crossover at 50Hz. From what I have seen this is approximately 10 Hz above the low end of your speakers FR, which gives adequate overlap to avoid "holes" in the FR.
Some subs have the ability to select the rolloff slope, most are fixed (slope should be in manual, but you may need to call - easy with PSA!

) SVS allows this slope to be either 12 or 24, and for the HTD's, 12 better matches the natural rolloff.
I think Merlin provides some very good "rule of thumb" principals, but think of it as a good starting point. I'm pretty sure their recommendations are based on speaker manufacturer specifications, which have plenty of their own variability. IOW, you may want to play with fine-tuning, but this should be a good start.