Some higher end (Expensive) receivers have network functionality and will can play music stored on a PC/NAS. Video streaming on receivers/amps is a relatively new technology and I don't know how effective it is. The likes of Sony STR-DA5500ES offer video streaming but cost £1300. The Sony site should have details and manuals for download.
Separates wise, you can stream music and video to devices such as the PS3 and
Popcorn Hour. You can find details of video streaming devices
HERE. The latest wireless-N routers are required if you want to go wireless. Homeplugs or cat5/6 are best for wired solutions.
Music streaming can be added relatively cheaply using Sonos, Apple Express or
Squeezebox. I use 2 x Squeezebox to give me cheap multi-room in 3 rooms of my house. My music (ripped in lossless FLAC format) is stored on an external HDD hooked up to my laptop which runs the server software. Details of music streamers can be found
HERE
PS. Cables and boxes are an occupational hazard of the AV hobby I'm afraid