for backing up you're mac I would use Time machine but others have been very fond of Super Duper and Carbon Copy.
Personally I would use Time Machine just because I like sticking to originals. Though some others like Super Duper/Carbon Copy because you have more options/settings on what you want to do.
As far as a NAS, I believe Time Capsule is the only way to go, unless you do as osxx said and get an Airport Extreme and attatch a usb drive to it.
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