Currently, I use a Mac Mini Server for streaming movies across the house to my AppleTV via Devolo AV+ homeplugs.
Also, I have a duplicate of my movie library stored on my ReadyNAS NV+.v2. Here, PLEX streams movies to PLEX iOS on my iPad3 via my Apple Airport Extreme. This still surprises me, given the relatively low powered ARM processor in the ReadyNAS.
A Squeezebox Touch replays my music library from my ReadyNAS.
Before returning it to John Lewis, my Sony KDL26EX553 had no difficulty playing-back movies from my ReadyNAS.
However, when the next iteration of the Mac Mini appears I will be selling my Mac Mini and Mac Mini Server for a fusion-driven Mac Mini (as my primary computer). Having tried a fusion Mac MIni in Regents Street AppleStore I cannot imagine buying a conventional Mac Mini.
That is why I am tempted by the diminutive Lenovo Q190 with combo Bluray drive as my HTPC (even though it has Windows 8). I can choose between PLEX, XMBC or MediaPortal for streaming movies to my television, or use iTunes/iHome Server for streaming movies to my AppleTV.