what center speaker to go with Kef 104.2

I would think a Kef 200c would be exactly what you need.
These are fantastic sounding speakers, i think it sounds better than my B&W HTM-2.
Hope this helps.

I'm going to put another 104.2 in the center to match. I have the kef 90 and dont think that it is a close match, as mathcing is so important in the front soundstage.

My post won't help, but I've been wondering the same thing. I have a pair of the early 90's vintage Raymond Cooke bi-wired 104.2s. Fantastic speakers. I assume the Reference 200c will work and perhaps even the older 100c. What will you be using for the surrounds?