Maybe the salesman was going with the idea that floorstanders don't need subs, which is largely not true (depending on what you're reproducing to an extent of course). Your M100s look like they need subs to me per the
measurements in any case, especially for movie soundtracks or bass heavy music. Matrixing music to multi-ch doesn't work for all music/tastes, so as was suggested, try just two ch mode for music.
By tilting inwards assume you mean toeing-in the speakers some? Some like to toe their speakers such that they cross at the listening position, some like it just behind the listening position, some before (combo of speaker and tastes) so some experiementation in position with toe-in and distance from walls is a good idea....
