The cross-over frequency is not only speaker-dependent, it is also room/location-dependent. Presumably you have a receiver with auto set-up capabilities. The receiver will find the correct cross-over for each speaker. Using that as a baseline, you can then experiment with different settings. If you have a sub, setting the cross-over to a higher frequency will relieve your receiver of having to re-produce the majority of the lows which will give it some more headroom.
The flip-side of that is that the channel bass the recording engineer intended for that channel won't come through the intended speaker which may reduce the A/V experience. Since I got my QS10s for example, my receiver found them at 40Hz and I've left them there. I've been surprised how much bass content comes through and how great it sounds.
Great choice on the speakers BTW!
