You say he can buy something else if the M80s don't scratch the itch. He may never have an itch because if he just puts the M80s in there, he'll like them because he won't have a basis for comparison. He's decided to contrast his M80s against a pair of KEFq100 which makes good sense.
I didn't think you tried multiple placement positions because if you had, you'd have noticed the qualities I described and would have made a different recommendation for Chaos.
By the way, I have 11-year old M80v2. I love them in my 4,200 cubic foot space where they are placed 9 feet apart, 6 feet away from side walls and 14 feet away from my MLP. I've tried other speakers in that room and none can do what the M80v2 does. I also have a 10x10x8 room with 2.1. In that room, a much lesser pair of bookshelves do what my M80s can't.
