I am biwiring, haven't compared it to single runs, but I think the most significant change in sound (and should be almost mandatory) is adding lead shot and of course, decoupling from the floor. I bent the supplied spikes all up, and bought more sturdy ones. But the difference was huge.
I have heard that biwiring makes a significant difference but haven't experienced it myself.
I am still trying to figure out the rear ambiance driver setting. I've been messing with it and it sounds good in different ways in different positions.