That's still 3 center channels, as far as speakers go. Sounds like a good way to obviate the left and right channels.

In any case, 350 watts/channel on average should be quite sufficient headroom wise, as it is extraordinarily unlikely that all 8 channels would need to peak at the same time. At least, I wouldn't want to be in the room when that happened.

I am the Doctor, and THIS... is my SPOON!