I chose the 60hz for two reasons. it's the point that the speaker starts to naturally decay off on it's ability to produce sound. Hopefully the receiver doesn't handle crossover points as a cliff that drops off to nothing, but as a point pleasantly decay down. Secondly as that is the point that the current requirements start to aggressively ramp up to drive the speaker for the lower hz sound.
Now if you are driving these speakers with a competent amp, then you can inch the crossover lower. The limiting factor for most is not the speaker but the amp that is driving the speaker to deliver clean power without clipping in a moving piece.
Axiom: ADA1000, LFR1100, VP180, QS8, EP500, M3, M3comp
AudioSource: Amp One/A