What kind of media server do you have or are you looking at? You can get one of those HP Microservers very cheaply (with the cashback deals) - for around £100. Stick a couple of large HDs in it and there's your media server.
The previous owner of my house spent quite a bit networking the house about 5 years ago - there's a nice wee patch panel and everything. He told me that his kids insisted on using WiFi so it was a bit of a waste in the end. We also only use WiFi.
