Most of the above.
My A/V system has been hard-wired thru-out the house for nearly 20 years. The "center" was originally the living room> then a "music" room> then an "Audio-Video Room" which of course is now called a home theater. Everything is intercontrolled with IR remotes and several IR repeaters. The HT has all the high end equipment (built into a false wall with access to the rear of the equipment) and 5 other rooms/areas (now known as "zones") have their own self-contained systems and are also connected back to the main Home Theater system with digital co-ax cable. All cables are hidden in the walls or under the floors and there's a lot of it). This was all pre computer.
My computer is actually in my workshop/office (which has an A/V system with a Thorens turntable) where I spend 75% of my waking time. Originally it was to be used for doing business and dowloading/scanning reference photos for use with my modelmaking business.
Then I discovered that I could preserve all my old music and store it all the HD(s)!!
. I added a SB Extigy and connected it to the existing digital co-ax cables and presto the computer was connected as another "source" in my system.
I now have a main monitor at my office desk and another at my workbench (with an IR keyboard & mouse) and another now in the HT room (connected by a loooong 40ft cable made up by my local computer shop guy) with an RF keyboard & mouse.
In the next couple of months this will be upgraded to a wireless network and some RF remotes for added flexibillty and access. Still gotta get Tivo too! It never ends....