2 streamers and one consolidated library. How?

I've searched and queried but what I'd like to do is somehow make it so that when I have 2 network media players running xbmc and streaming from the same source [server in the garage] that when either one is running and scans. It updates the library to both? But mainly for telly so it can state "watched" on episodes watched by either without having to manually do it on the other

Does that make any sense?

Also. Would there be any benefit keeping fanart/covers/etc on the server than the player? I know it does this for telly but it seems that movies posters/fanart is stored locally?

Cheers