For what it's worth, here's a thread detailing a budget open baffle line array build of mine from last year. I used cheap $3.00 foster wide range drivers (sadly no longer widely available) , cheaper Apex Jr tweeters and much cat 5 cable (yes, I'm cheap) crossed over around 5 KHz (lower would've been better, but I didn't want to risk incurring nasty tweeter distortion modes).
http://www.diyaudio.com/forums/showthread.php?s=&threadid=99960
This design (being open baffle) needs a subwoofer below 60 - 80 Hz (I use a Fitzmaurice TableTuba Horn Subwoofer) and the combo plays way better than the amount I spent on it. High efficiency is the way to go.
Impedance is about 6 ohm and efficiency is the mid to upper 90s.
