As for horn loading, it's a great way to go, particularly for the frequency range you want to cover. But it does make the cabinet larger, and if you're playing clubs, you may find basshorns to be a bit much to carry alone. Some of my musician friends like bigger cabinets, and some don't. I suppose a lot depends on where you play and how you like to setup.

This is a good discussion for the Musical Instrument Speakers forum.

I finally completed a bass cabinet using ported cabinet and a
15" JBL M151 driver. This is essentially a 4-Pi without a horn.
Sounds great to me. 4K-5K is stretching it for many of the
Eminence drivers, except for the B102's. Those are 10" bass
speakers that have decent specs. you'd have to model them to
see if they met your needs. Each is good for 200W. I'd go for
a pair. Have you checked the eminence site for specs?
http://www.eminence.com/
Chris

If you need any software to help design the cabinets, there are some great programs in the "info" section of the π Speakers website. Look near the bottom of the page and you'll find them.

Keep us posted on your speaker project and post some photos if you can when you have them finished!