The receiver's job is to decode audio being fed to it digitally, then accurately amplify that signal to your speakers.
The TV's job is to faithfully recreate the video signal which is fed to it.
Neither of these devices job is to stream your home media!
Even when it is built into certain devices you are talking about a $20 chip embedded with added functionality that is supposed to decode, navigate, and deal with your home network... In simple terms, it barely works (if at all) and it is never a good experience.
What you want/need is a dedicated box which does exactly what you want. Just like if you want to watch HD cable/sat you will have a box for that. For Blu-ray, you will have a box for that. If you want to stream stuff off your home network, then you need a good box for that.
Popcorn Hour, Dune, AppleTV, WDTV, and a fairly long list of others all have some capability to do this. Popcorn Hour and Dune, IMO, lead the pack for completeness and versatility.
Home Theater PCs are also used frequently, but they are NOT complete and require a great deal of end-user involvement to get them working perfectly. They hold the most potential and most versatility IMO, but they are generally fan cooled which adds noise to the room, and can have a pretty hefty price tag for top tier functionality.
I use two Dune products, and their basic interface looks terrible, but works well. Their cover art skins (Yadis for me) look great, work well, and took a while for me to setup, but the family loves it, and uses it.