By having the identical tower, you will be:
- perfectly matched as matched can be, in all speaker characteristics
- even plane of tweeters/drivers for perfect and even panning
- completely bypass horizontal lobing issues inherent in a horiz mtm design, which usually means a sweetspot at less than 20 degrees.
- horiz cabinet means vertical dispersion as opposed to horiz dispersion. Sound likes to travel along the path of least resistance (smallest dimension), so to speak.
- less stuff/mass/material in-between your speakers that would otherwise destroy stereo, or m-ch, imaging.
- better video immersion without all the lights up front
- best of all, money in the pocket
If it indeed must be horizontal, the best designs will be such as top mounted tweeter (ie B&W), WTMW (ie Revel, AV123), or coincidental (KEF).
Now, if you have only one loveseat, for 1-2 viewers, not as big of a deal, assuming you sit straight on. If you have more than one couch, my suggestions just only regarding center design will benefit you greatly.