DTS is much stricter in their sound placement. So, absolutely, get a center channel.
Also as a note, there's another forum going on about small vs large speaker settings. It a touchy subject. Personally I think things sound better in Large. With Dolby Digital you get away with Large and not miss much, but with DTS, they still send some pretty low end info to the center and surrounds (lower than Axiom speakers go), so setting them to Small is recommended in this case (if you're all about the bass).
