That's quite high in my opinion, I'm pretty sure you'll be able to localize a good amount of bass like voice and the such that should be coming from the center speaker. The crossover doesn't have to be set down at 80Hz, it can be anything that you like. I would suggest setting it around 100Hz and then playing with it up and down to see what works best for you.
I have a slight gap around 100Hz in my setup but that's because the little JBL's just can't go low enough to match the sub without localizing male voices and the such. I'd rather the slight dip in volume then the annoyance of hearing male voice from the floor next to my TV.
Overall play around and see what you like.
PS: I hope all of that made sense I'm watching the Phantom Menace as I type.