Don't just get an analog x-over, the way things are now days why not go to a digital x-over(DSP, also known as speaker management systems). For a few dollars more there well worth it, on many of them you can control the x-over slopes, time align, etc. etc., a lot more than you can do with just an analog one.For example here some pretty resonable models:
Behringer Ultra Drive Pro DCX2496 for $250
DBX Drive Rack PA for around $400
DBX Drive Rack 260 for around $750
Shop around and you can find some deals.
HTH
Bill W.