NAS recommendations?

[mft]

Following lots of nudges from various sources (including here!) I'm going to invest in a basic network attached storage device for regular backups. I presume I can ethernet one of these into the back of my wireless router and back up all of the house PCs wirelessly?

Once I've got a basic backup routine sorted, I'll back that up to DVDs periodically too. Is it worth shelling out for a NAS that can RAID internally in case a disk goes down, or is this unnecessary?

Any recommendations which one to get? There is quite a choice out there, and lots of them have mixed reviews from different places.

Thanks