If it were me, I'd start with the center and surrounds crossed over at 40Hz and the fronts set to large (completely full range).

You might also play with crossing the surrounds over at 60Hz and see what it does. Do you have a sub, or are your mains handling all the low frequency? If you do have a sub, you might experiment with crossing the fronts over at 40Hz too, and maybe even bump the center up to 60Hz.