In reply to MG:
As I suggested here -
http://www.ukclimbing.com/forums/t.php?n=603225#x7931829 - it might be worth taking a look at the spec for your router. The Technicolor 582n supplied by many ISPs has a USB port that can take a USB hard drive and create a network file server and DLNA media server... Whilst the manual says that NTFS support is 'optional', it's obviously not a fitted option on my Tesco-supplied router. So there's a 4GB file size limit imposed by FAT32 that it does support. Certainly worth a bit of a play.
Then you'll need a Digital Media Renderer; a bit of electronics connected to your network (wired or wifi) running software to receive a media stream and convert it to audio. The bit of electronics can be anything from an Android phone or tablet, through to stupidly expensive audiophile things, and the software might be something like BubbleUPnP, costing £3 or so. If you have a smart TV or smart Blu-Ray player, they might have DMR functions. Again, worth looking at the specs of what you already have in the house; look for 'DLNA' or 'UPnP' in the manual.
I'm currently part way through this process, and still looking for a cheap hardware platform for the renderer:
http://www.ukclimbing.com/forums/t.php?n=603783
I may investigate one of the small Linux platforms like Gumstix or RaspberryPi, or buy a cheap, dedicated DMR from somewhere like 7dayshop, or even buy a cheap, 2nd hand Android phone, maybe with a broken screen... After all, I'm just after the headphone socket...
I've been using MediaMonkey to manage and play my music for a few years now, and the library now lives on a small NAS. New CDs get ripped and added to the library via MediaMonkey, which also plays music when I'm working on the PC.
There are many 'UPnP Players' out there, but most of them are actually Digital Media Controllers, which read the database held by the Server, and instruct it to stream media to a DMR. Linn Kinsky seems quite a nice, simple, free DMC, and can control streaming to multiple 'rooms' (actually, to multiple DMRs, but on the assumption that you'll have one DMR per room). I've had three Android tablets, each playing different music, controlled by Kinsky on an iPad...
The cheapest way to "go digital"? Buy a 3.5mm stereo jack plug to stereo phono plug lead from your local pound store, plug it into the headphone output of your PC/laptop, and plug the phono end into the Aux input of your hifi. Use one of a number of programs to rip your CDs to HDD, manage your music library and play music. I would suggest MediaMonkey. I would not recommend iTunes.
It does need the PC to be on to play music, of course, and that's what drove me down the NAS route; small, low power box, always on, ready to stream media. Can even stream remotely if you pick the right NAS and enable remote access.