Using 2 of Centers as Bookshelf Speakers.

Sell the extra speaker, two separate speakers as a center is a bad idea.

I could be wrong, but I think the OP is asking if a speaker originally designed as a CENTER can be purchased as a PAIR and used for a STEREO Pair.

I don't (and I could be wrong) think he is asking about using two Centers in a CENTER CHANNEL function.

I think the OP is considering purchasing a 2nd center to match his existing one and using them as a stereo pair. If it's a second system I'd certainly take the chance of it sounding pretty dang great.

When I was speaker shopping with my father-in-law a few months ago one of the high end stores we visited had a salesman and inquired about his room and intended use. He actually suggested using two LCR speakers in some situations. Speakers are speakers at a some point. They either sound good or they don't.

The Focal CC 800v isn't ported like the bookshelf speakers in the Chorus series are, but having two 6-1/2 inch drivers should provide plenty of bass.

I sent Focal a message questioning in this regard but no reply from them...