Hi Ravi,
i'm still battling with this options at the moment myself.
I have not come across any real HD solutions, they are mostly composite and somtime svid.
I'm currently still on the - 'disttribute over IP' and decode at the end point, with either 1 or 2 server PC's to handle the encoding/hosting of MP3's,vid's, pics etc. (LinuxMCE / MediaPortal/ Windows Home Server etc.)
With a wired gigabit network there is plenty of scope for the future and there is currently a drive for more and more HD clients starting to emerge - sling catcher one of the eagerly awited ones.
bottom line I feel is that run a good few cat5's to all end points and you should be able to handle mostly anything. You can get balun's to covert mostly anything to cat5 - Keith's being one example, madnat housing more (including spdif) - I have also found hdmi baluns. Stick with the cat5 and you should be good.
Another good suggestion (personal) never believe anything sky 'technical' tell you - I've never had them tell me anything that made sense or was correct.
Cheers,
Ian.