Subwoofer setting

The 50 should be good since there will be some overlap as the low end of the mains rolls off, the sub will roll off in the opposite direction.

General rule is 1/2 or whole octave above the main speaker's -3dB point. Unfortunately, the spec you quote does not tell us that but, assuming 60Hz was the -3dB point, I would recommend 80 or 120Hz.

Kal

I follow Kal's logic, but I would lean towards 80 or 50. 120 is way to easy to localize. I feel the lower the better unless you feel like you are missing something. Placement can also effect performance and volume. Placing speakers and sub equidistant to the listening position will ensure proper phase. Near walls and corners will increase volume. Many threads and opinions on this in the forums.

As much a question as an attempt to add to the discussion, but doesn't the in room frequency response of the mains have something to do with the subwoofer crossover point? Or is that just considered a given?

Yes, the in-room response is quite relevant but the vast majority of people have no way to measure that and must rely on the printed specs, if any.

Kal