You have a real world system and kudos for selecting Vandersteen 1Cs. If ever there was a well-designed and made, solid entry speaker that is phase and time aligned, the 1Cs are it. I have a pair too. The room is one half of your sound. Focus on first reflection points at the side walls and ceiling, perhaps place a couple of absorbers there and one or two diffusors either between the speakers on the front wall, if possible, or on the back wall.