Regular sierra-2 for center?

[Blutarsky]

Is there any advantage to rotating the tweeter of my Sierra-2 Center and using it vertically?

[monkuboy]

Is there any advantage to rotating the tweeter of my Sierra-2 Center and using it vertically?

Probably only if using it vertically would put the drivers in the same horizontal plane as the ones in your left and right speakers.

[davef]

Is there any advantage to rotating the tweeter of my Sierra-2 Center and using it vertically?

You would get wider and more symmetrical horizontal dispersion. Ideal if listeners are sitting horizontally off-axis, but it won't make any audible difference for those sitting on-axis.