Hi Jerrod.The JBL's look pretty good.
A small box required with a sensitivity of about 101 SPL. I notice JBL goes out of their way to say the sensitivity rating isn't done on a 1Kh tone, it's done on a sweep of a range, and it may be higher sensitivity. ( http://www.jblpro.com/pub/obsolete/2123.pdf ) That's good. I used a PHL midrange with a rating of 97 spl and used L-pads to take the top horns down. Now that I've heard them I would have liked a closer SPL match like the JBL will give you.
You'd probably want to cross these at under 500 on the low end and JBL suggests 3000 as a max high crossover. A lot of people like to go to 3500 for the high end from what I've been reading. That will keep voices on the same driver for the most part instead of splitting them. You might get away with resistors to tame the top end, you might need l-pads. (maybe tri-amp ;-).) There also seems to be a lot of talk about some mid-range horns showing up at some point which may be worth waiting for. You'll probably want to at least bi-amp because the low end on the corner horn is very strong and the best way to balance it is to put the low and high end on seperate power sources.
I used the non-horn midrange because I just use my Pi 7's in my living room and with the high SPL midrange they're more than enough for what I use them for. The guys doing professional sound would like to stay with horns because they want the power. My ears tell me the non-horn midrange has a better sound stage than most of the horns I've heard. (I "might" be asking for a fight here ;-) ).
Feel free to comment Wayne. These are just my (limited) experiences.
Have fun,
Grant.