I have an Onkyo a/v rated for 6 - 16 ohm speakers. If I were to use an (8 ohm center channel speaker) in a (5.1 surround speak

[Lann_]

using a center channel speaker in a surround position.

 

[americanaudiophile]

You could use two centers but a single one would not be the right way to go. The impedance is fine.