The whole room matters, especially in non immediate reflection points. I'd talk to GIK who can give you great advice and products, but it depends really. If your whole room is well damped, rug over slate will work, but if the additional glass means you will be short of necessary absorption, go with carpet.
Also, one overlooked area for absoprition is the floor between and behind the speakers. Damping this can often lead to a smoother sounding treble.
Also, one overlooked area for absoprition is the floor between and behind the speakers. Damping this can often lead to a smoother sounding treble.