Still odd to have your QS8's being set that high but I would suspect it is just your room/speaker placement causing an issue.
With Audyssey setting the crossover that high simply means it is seeing a substantial drop off below that frequency from the QS8's so it wants to send anything below that crossover(rolled off not a brick wall) to the sub. Since this is just a surround channel I wouldn't worry too much about dropping that crossover on them to 100 or even 80.
I would suggest having a listen at all crossover points from 80 to 150 and then go with the one you liked the best.
