I totally agree with what Jay said earlier in this thread. Here's my additional 2 cents.
I've heard the NX-Otica without subs, and I was impressed at how low they went. Even in Don's big open room they were pretty solid, so I could see some people could happily using them without subs. I have a pair of MTM's, and I would not recommend using them without subs. However, I've heard both the NX-Otica and the NX-Treme, and I'm completely happy with my MTMs and subs.
The subs are insanely good though, and really easy to integrate. So, +1 for getting subs first.