help on center speaker

I am in the process of upgrading my system to 6.1 channels. I just got my NAD T753. I have front Linn Index speakers and just purchased Linn Unik for the back together with a Linn Afekt sub. Can someone recommend me a front center speaker to match with my current Linn speakers? I heard that Linn Centrik will be the best match (discontinued model). Will any other brand work for my setup or should I stick with Linn? Maybe KEF? Or maybe I won’t make any difference at all? Any ideas/comments are welcome.
Thanks a lot!