A corner of the room has a prominent slate slab and I must place the Theater 7 at 2" from this corner. Is this a big problem?

I have a 3m x 7m room and i must put the speakers along the short wall; has anyone a suggestion of which set of speakers would be the most appropriate to my room (i think the Theater 4).

Regards from Italy Angelo

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.