I love the 6Ks too! I realize space is tight, but how far do you have them from the walls? Pulling them forward from the back wall (even a little bit) should help. You can also try adjusting the bass by -1 or -2 and see if that helps.

I think you are asking the right questions and are smart to try everything you can to get them to work before selling them- they really are wonderful speakers, and worth the effort to try make them work IMHO.

Hope you get it sorted!

Theater: 861v4_LPS, 818v3, HD621, Oppo 203, Lumagen Pro, DSP8000SE, DSP5500C, SW1600x2, DSP5500, Epson 6040UB, PS4
Living room: 861v4_LPS, HD621, DSP8000SE, DSP5200C, Oppo 203, Lumagen 2143, 818v3, Sooloos/MC600 Bluesound Node
Bedroom: M80
office: G68D, DSP6000
Garage: DSP5000
Storage: M33s, DSP33s, DSP5k, 501, 518, M1500, G98DH, SW1600