Your old computer (if you upgraded that per your previous post) could also act as a server. I expect not the most eco-friendly approach. If your statement "my CD collection would fit in a smaller space" means you don't have a large music collection, why not keep it on your current iDevices and save the (c.£300) you would pay for a NAS. Unless the NAS serves a secondary benefit - such as back-up or the like? A lot depends on what you want to spend, and what you want it to do. If you wanted a dedicated source - what about an iPod touch?