The seven π cornerhorns present a very flat impedance curve, so I expect your amplifier will have no trouble driving them. The Theater three π is an excellent speaker, but impedance peaks in the bass range are a little higher.

I prefer to place cornerhorns at opposite ends of a short wall in rectangular rooms. I prefer this on rooms with 5/7 ratio or so. You're is a little bit more narrow than that, but this only makes it even more important that you place them on the short wall. What this does, is makes the best listening area in the first 3m back from the wall where both speakers are.