Yeah I forget the exact details but I think the two locations are as follows:

to adjust the crossover for surround use during movies: Manual setup> crossover frequency. Try setting the FL and FR to 80 HZ.

For the Stereo setting it is not under manual setup. I believe it is in Audio Setup->2Ch direct/stereo->crossover. See what they are both set at and try moving up to 80 hz if they are not already there.

-David