Sheik_Yerbutay,
Your 807 WILL stream MP3/FLAC and other audio format - your AVR manual says so
About video part - you get me confused
807 doesnt stream video at all... If you intend to stream video to your HT you'll need additional media client - like Boxee, PCH or WD TV Live
and all of clients I mentioned above will play streamed 1080p content w/o transcoding.
You Home server task would be only to serve files, so don't worry about cpu performance....
Technically any PC will stream media (like Flacs) with DLNA server software installed - like TwonkyMedia etc...