For what you describe, there is no set-top box, so HTPC is the only solution. Subtract the tuners/DVR, then you have lots of choices. The best regarded streamers are Dune, Popcorn Hour and Mede8er. Re: 1080p over wifi, forget it if you'll be streaming 1:1 1080p BD rips, but possible if they're lower bitrate re-encoded files.
As for exactly which streamer to recommend, you'll need to provide some of your expectations for local media. Need HD audio? Okay with a movie/TV show jukebox that necessitates setting up/managing via a PC? Can do w/o Netflix, Amazon, etc.?
Hi-deft Media Keen Videosaurus