Anonymous is correct. I'd recommend 80 as the cross over, however I think we really need to know what you are using for mains. That is going to have more of a bearing on your cross over than the center. For example, if you are using Beta 50's, they can get pretty low and maybe you would be better served with a 40 or 60 cross. Also, how is your sub hooked up? LFE or speaker level. It matters. Good Luck.
Right on for the info. I had it set to 200 instead of 60, thinking it was the closest thing to what the speakers said but i was wrong. My mains are just some old sony ss-mb215 that i had. One day i will get some beta 50's but not until i save some more money. My sub is hooked up LFE i guess. i used the old coaxial cable that used to hook up the audio from the DVD. For the dvd connection, i use a fiber optic cable.