The center speaker will not effect the Plasma. Enjoy!!!
It should not have a effect. but consult both the speaker and TV’s owners manual for more detail. You also could disclose both model numbers to get a definitive answer.
The center speaker is shielded.
I don’t know if speakers can interfere with a picture of a Plasma TV, but to be on the safe side of things you should make sure your center speaker is magnetically shielded.