It would be silent in operation, and connect to two or more external USB hard disk drives – the USB disks would hold the music files. Much of my music archive is stored in the .flac lossless format. (Might it be a better idea to look for a 'silent' NAS case and connect via Ethernet? I suspect so – my plans would use both Pi USB ports for other things.)

Ultimately I would look to transferring the music to solid state drives, but that is very much a 'part 2' of the project.

I would like to be able to access the Raspberry server wirelessly in order to select the tracks to be played. This access may be from my laptop, PC, or smartphone.

The music would be taken from the hard disk and streamed out of a USB port. It will then be converted externally using a USB -> S/PDIF converter (I've asked a question about this in the compatibility forum), which will connect to a DAC. I have the converter and DAC part of the system already in hand, and can use it with a PC or laptop running Windows; I currently connect a HDD to my laptop by USB, and use Foobar to play music, output being via USB to the USB -> S/PDIF converter.

Is what I would like to do a practical idea? I'm not a programmer which may restrict my ability to make this work!

I don't think that a lack of communication on your part is necessarily responsible – I have to confess to suspecting this would work, based on research I have done, but hadn't found a definitive confirmation. (Which I now have – thank you.) I've also not read the manual (I will), but I have read many anecdotal reports of eventual success.

The only issue I may have is wiring the NAS /and/ the Pi to the router as they are in very different parts of the house. Could the music files be transferred wirelessly to the Pi which would be wired to the DAC? (In my case, it would be USB-connected to the USB -> S/PDIF converter.) In a perfect world, the Pi would 'read ahead', buffering the file in memory before playing it – the 512Mb version could conceivably buffer an entire album in lossless format. However, I suspect there is a programming need there, and that is something I currently lack the skill to perform. (Help!?! )

Please bear in mind that I don't currently have a Pi; I've also been looking at ODROID. I feel more comfortable with Pi, and know people who have used it for other purposes including home automation projects (something I hope to do another time).

Irrespective, there's definite mileage in exploring this further.

Thanks.