I was thinking this too myself last night, maybe some already do exist, but I wondered why are they not any WiFi amplifiers when it comes to the traditional 2 channel amplifier.

I thought this because I was playing with new Sonneteer Server last night which I'll have more on later and thought there is no way to play direct to a stereo amplifier as they don't pick up a WiFi signal.

Until amplifiers have this feature I think servers may struggle to get a real grip on the market, am I on the right track with this?

I changed the title to UPnP as put I wrong, I wonder you PC geeks thought on this?

Here's what it is

http://en.wikipedia.org/wiki/Universal_Plug_and_Play

You would need a wireless receiver, plus a dac built into the amp.

The best solution to this at the moment at a reasonable price is the Linn Majic dsi it is awesome @ £2500 they also do another called the Acurate I think and that is £11,500, basically upnp with a dac and an integrated in one box, I almost scrapped my entire hifi for one, but then I couldnt fiddle in the future but I am almost gunna buy one for another system!
http://www.moorgateacoustics.co.uk/linn-products/linn-majik-dsi-2087903-395866-.php

The good thing about this type of interface is that with an ethernet connection the data being recieved by the amp is then error corrective, as a data flow over tcp via a cat cable with correct itself and should give a perfect full bandwidth digital signal unlike coax or optical and can carry a massive amount of data upto 32bit if neccessary

It makes sense to me, I guess it's just a matter of time before it become implemented more.