Sounds like you should be able to use the CD player as a DAC if it has an optical input - just run a TOSLINK cable between Squeezebox and CD, rather than using the Squeezebox's analogue outputs, and you'll be sorted.
The NAS connects to your wireless router, usually via an Ethernet cable. so they normally need to be in the same room as each other. I've not looked for over a year, but QNAP seemed highly regarded as a manufacturer. Just check that it can run the SlimServer software (or whatever they're calling it these days - I forget).
The Squeezebox has a wireless adapter built in, so it can go anywhere. Mine is perched on the subwoofer, next to the hi-fi rack, while the (noisy) NAS and wireless access point are well out of the way upstairs.