2x6spds dining room isn't much different from my living room in terms of "interesting" combinations of materials and dimensions. The tiniest change makes a difference:
Sound & imaging are fantastic with this setup (ignore the blur):
but dead and lifeless with this setup (blind on right hand window pulled down, sofa cushion moved down to floor):
BTW I just ordered a pair of M3v4 refurbs so I can do something a bit more like an apples-to-apples speaker comparison. I have always really enjoyed M3's every time I get a chance to listen to them.