Hi McPillager,
I tested some Media Server with my TV:
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TVMobili = It can be downloaded from www.tvmobili.com.  It is very simple to use and easy to install. Also, it is lightweight.   It runs on Windows, Mac, and Linux.
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Serviio = It can be downloaded from www.serviio.org   Like TVMobili, it is simple and easy to use.  You must select "Samsung C-Series" from the profiles sections in order to display the subtitles in your TV. It can't automatic select the TV.      It runs on Windows, Mac, and Linux as well.
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Samsung PC Share Manager =  it can be downloaded from Samsung's website.  However, it required to much CPU processing and the refresh process takes a lot of time.  Only for Windows.
There are more Media Server in the market, like Twonky*, Wild Media Server, and Mezzmo, but you have to pay for them.
* TwonkyMedia Server is excellent Media Server, but It DO NOT support external subtitles. According to their Development Team, UPnP & DLNA don't have any specification about subtitles.  That's funny!!!  All the other Media Servers that I listed support external subtitles!  It's not about specifications, it's about transcoding!!  
 
 Regards!