3 way, coax in the middle (or, if you have the space, tweeter above midrange). See:
- Infinity RC263
- SVS Ultra Center
- KEF R2C
- Revel C52 (this is quite expensive)
Look at the RC263 and Sierra Horizon reviews, the horizontal performance is similar.
Then look at the CBM-340 review, the horizontal performance is terrible, I think the red in the polar plot was like +/-10° at the worst.
Facts of life are that tradeoffs are the name of the game for center channels that need to have limited vertical cabinet size in a multich system. There's also the fact that we're talking about "home" systems, not a real theater. For folks with the ways and means to build a
real HT, they will have a large projection screen and the work-around options to not be stuck with these compromise MTM's.
At my place the beaming is a non-issue, there's only one real seat,
mine. Guests sit on the couch on the side wall and every one of them to the man/woman are blown away by the sound quality cause they wouldn't know a FR aberation if I hit them in the head with a 2x4. LOL. The very occasional VIP guest gets to sit in my seat. But isn't that the way of all HiFi demos, stereo or multich" whether at a dealer, hi fi show, or a fellow audiophiles house, they always want you to sit in the "sweet spot" to really appreciate the sound.

The 4500 blends incredibly well with my 4 3600's and at the end of the day isn't that the real goal.