Thanks for your responses.
@CatBrat: I've read different accounts about the merits of the center above the screen. The height of my screen is about 5 feet and the screen is maybe 2.5 to 3 feet from the floor, which would result in a center placed over 7 feet from the floor, which seems kind of high to me.
In order to keep things simple, I don't want to use risers for the seating rows, just place the seats staggered. I would place the center speaker under the screen, but high enough that it is visible from the seats. BTW, the screen is just a straightforward fixed screen.
I've also read pro and con opinions regarding one or two center speakers, and two would be more costly than using a single 160.