It would depend on the woofer you are using. But using Altec woofers, I'd say 800-1200 hz would be more appropriate. Any good Altec woofer should reach that high easily. You can cross the tweeter over at 500 hz but power handling will suffer some. Depends on how hard (loud) you are going to listen to them. Power handling really shouldn't be a problem seeing how efficient Altec horn drivers are anyways. In a normal room, the 902s should be really loud with only 10 watts each going to them. I personally think that they just sound better crossed over a little higher than stock. They don't sound as honky that way; a little more refined to me. I'm sure someone else that has more experience will help more than I can. Good luck and enjoy...