Backup solutions

Since I started working exclusively on laptops, I’ve been backing everything up to a 500gb external hard drive. This is working well, but I do sometimes miss having an “always on” desktop computer that acts as a repository for everything I’ve ever owned. I keep toying with either buying or building something to fulfil this purpose, but I’m not sure what is actually required. I could go for some sort of NAS solution but that would take away the joy of actually building something myself, and I think for £260 I’d want something I could occasionally use for tasks other than storage. I was also looking at the Zotak Z-Box, which would be quiet and energy efficient, but which only takes 2.5″ hard drives (and thus would be more expensive per Gb of storage than a desktop solution). I suppose what I really need is a couple of 1Tb hard drives in some sort of shuttle setup. I’d also (at some point in time) like to experiment with pairing a Zotak Z-Box with a decent sized SSD drive which should result in a low-consumption (fairly) fast PC that would make a good long term successor to the ageing Mac we use as a media centre. Of course, this is not a good time for me to be thinking about buying computers, and I should probably think about how best to utilise the ones I have to solve this problem.