With 24 TB of videos I'd have to do too many video conversions. I just use VLC for most things. VLC will even de-interlace video files (I have quite a few old interlaced video files) which is a great feature.
And I have too many videos to want to want to go through all the XBMC or Plex stuff. I like to have the Mac desktop so I can see all the drives and go right to the file I want to play. It may not be as "pretty" user interface wise, but it's a lot faster finding files.
But, for now I use my iMac to watch videos anyway. I haven't had a TV in close to 8 years. I may buy a big screen TV this year. If I do I'll buy a Mac-Mini to feed it video.
As always, YMMV.
ive only got half a gig of media, so we are totally different ball parks!