You can do this using Media Center extenders. The V2 extenders are high def and support Vista MCE. Here are some that are available now:
The Linksys DMA2100 is a unit without DVD, has Highdef support (HDMI, component), is silent without a fan, and it tiny. It supports Wireless n & g/b, it comes with a nice universal remote which can control your TV and extender at once. The linksys can stream content from UPNP media devices or network attached storage, it supports some additional codecs also - XVid, ISO, DivX, MPEG4 (Advanced simple profile only) and consumes just 16W of power!
The Linksys DMA2200 is the same as the unit above but comes with an inbuilt upscaling (720p, 1080i, 1080p) DVD player.
The D-Link DSM-750 is a very thin unit, but in the style of an audio/video rack device is about the length and width of a VCR. It has similar features to the Linksys devices. Again this unit supports High Def (HDMI, Component) and supports Wireless n & g, it also has DLinks media lounge software and can be used to play media from other sources other than Media Center. It supports a few additional codecs through media center such as H.264, xvid, MPEG-4 AVI's, MPEG-4 (Advanced Simple profile only) and consumes an amazingly low 10w of power. (Again the dlink is silent and fanless)
The prices range from around 200 bucks to around 400 bucks. You need to weigh up what is important to you, some people compare the 360 price to the extenders but the extenders have additional codec support, fanless operation, low power consumption and inbuilt wireless. Obviously though they do not play games 
The price is actually exceptional when put into perspective of what you are doing, these devices are very new and full featured, and when you compare the fact you could get 4 units for around the price of a fully loaded Tivo 3 unit and have a total unsurpassed integrated experience throughout all your media in every room of your house it really does work out a nice deal.
The design of your media network also should be considered, my recommendation would be a dedicated media center pc which outputs directly to the main tv in your house and then extenders in each bedroom. (Maybe in place of 1 extender, say have a 360 in the kids room and hit their gaming needs there to), In the kitchen you could do an extender, which is what i have, but you might consider having a laptop or tablet pc available to the kitchen, that way you get the added benefit of having a browser available to the kitchen. You can also access your recorded tv (non OCUR content) through Windows Media Player 11 on a tablet.