You could go down the route of building a cheap HTPC. I'm planning to do this in the future. I think with a good sound card that outputs a digital signal and a DAC there is no reason that you shouldn't get the quality of a £500 - 800 CD player plus all the functionality of a HTPC.
It shouldn't cost too much, as far as I can tell all you need is a good motherboard and a big hard drive. the processor speed doesn't seem to be a big factor.
Plus there is the added knowledge that you can easily upgrade when new technologies become available and your initial investment wont be lost.
I use a modded second hand xbox, running xbox media player as a video and mp3 jukebox. It can play mp3's off of my ibooks or its own harddrive, or internet radio as well as DIVX videos. You also have the advantage of being able to use a remote control and can connect to a TV to change tracks if required.
If you get the advanced AV cable you gain a digital output which sounds very good through my Arcam Black Box 5 DAC. All in all it cost me around £120 which is a bargain IMHO
forget looking for hifi with Wireless built in - this isnt the way to go at all.
My suggestion would be.
Shop around and buy whatever hifi solution you are looking for with the sound that you like. (or keep your old one!)
Then Add a Digital Media Adaptor and plug it into the 'AuX' input on your hifi/amp.
There are several DMAs on the market now... some need a TV connection so you can see the menus (linksys WMA11B) . but others have an LCD or VFD display, so they are easier to use just for music - (linkysys have just announced an audio only unit, and Netgear have the mp101 media player which starts hipping next month).
If you want a unit that can do more than music - take a look at the pinnacle showcenter.
All of these options just connected to your exisiting wireless LAN...
This isnt an exaustive list by any means.. there are more appearing every day (and more planned to be announces at Cebit), but will give you much more flexability that looking for a integrated system.
Actually, come to the conlcusion that a Wireless Media Adpator is the way to go, Linksys do one, aswell as Streamium BUT as yet - I need one that enables me to get it to connect to a LInux server, and get MP3 from there. The LInksys one defianaltly does not as it needs Windows software.