NAS or external hard disk for SQ Touch based syste

I'd like to back up my digital music (and photos) that I currently store on my iMac and stream wirelessly to my main system via a SQ Touch. My sense is that an external hard disk would be simplest. But I'm wondering what a NAS device would do for me. Are there reasons to prefer one approach over the other? I've also read that it's possible to connect a NAS directly to the Touch. Are there sonic (or other) advantages to that. I'm not really clear about the difference between a NAS and external hard drive, so some info on that would be greatly appreciated
Just get a large external HD and connect it to a Firewire or USB port on the iMac. Then designate that external drive to be the Time Machine disk. From here on out, the operating system will automatically keep backups of the system on that drive, and let you go back to see how the files looked at any given time in the past. It's your easiest and cheapest option.

You can theoretically accomplish the same thing with the NAS, but it involves a little more trickery (ie, create a sparseimage on the NAS) and you will incur network latency with the NAS, especially if you don't have a high-speed wired network.

The difference is that an external hard drive is designed to be connected to a particular COMPUTER, and that computer can, if it chooses, share it to the rest of the network. An NAS, on the other hand, is connected to a particular NETWORK and shares its storage with other computers on that network. So the NAS has additional logic and network interfaces that allow it to function in a network environment. Now, if you wanted to access these music files from multiple computers and you had a high-speed network, then the NAS starts to make some sense. Of course, you would need to back it up in some way, so you would need an additional NAS or a computer on your network with an external HD to back up the NAS.

With the iMac, the external HD can be configured to automatically back up the files inside the iMac, so this is by far your simplest option.

There is a lot of information about storage devices on the Squeezebox forums, so I would recommend you take a look there.

One of the major differences is that a NAS device has a small processor and operating system. Many come preloaded with the Squeezebox server software, so the NAS can serve all your music files without the PC (or Mac) running. They can also come with multiple drives that can me set up in a RAID configuration. Overall, more powerful, but also more complex.