The JBLs better mate with your center channel, assuming the center channel has ceramic type tweeters.
The Phantoms are alright and I would prefer them to the JBLs, but the JBLs are more efficient. I don't really enjoy listening to the Performance series, not really a sit back and listen to music type of speaker IMO, then again I would say the same about the JBLs, not trying to be offensive.
How are you getting the Phantoms?