actually, the ksb 1.1 is rated, 2.5 db down, at 91hz. given that it's a 5.25 bass driver, i think i would try a higher high pass point.

imo, you definitely have enough power to land those 5.25 speaker cones onto the floor at 80hz high pass.

also, if you listen to sacd or dvd-a, no high pass is applied digitally, so definitely switch ON the analog bass management toggle on the back beforehand. also, the 6 channel bypass level is higher at -10db than digital surround formats.