I'm considering purchasing a SuperCenter XL to match my Triton One's. My question is positioning for best sound quality. I've read some recommendations favoring placing the center channel just above the TV as opposed to just below the TV. Any thoughts on this ?

Above the TV is a good choice if you have multiple rows of listeners (that way the front row doesn't block the sound for the back row). Otherwise, no difference, and most put it below as long as below doesn't block the picture. Just make sure to angle the speaker (up or down) to point at ear level, and keep it clear from reflective surfaces/edges.