I have a version of the Pi 7's where I substituted my own drivers. This design is very efficient and it's hard to believe how powerful the bass is with corner loading without hearing them. They play loud very easily. I bought the boxes for these and didn't build them but have built some Davids from Bill Fitzmaurice since then which are a much harder build than the Pi 7.Someone mentioned in the responses to your email about making the speaker look smaller. LOL LOL LOL LOL LMFHO (laughing my fool head off) OUCH ! These ARE NOT small speakers.
If you can spend a couple extra bucks go for the good drivers. I've never heard the JBL's but wasn't happy with the Emminence Delta's I had in the original Theatre's. Mind you I didn't pair them with a tube amp which may be a different story. On the other hand it would be nice to be able to change amps if you felt the urge (eg. you want to take them to a party).
Have fun,
Grant.