Buffalo does have RAID network drives, but they’re a lot more money. The LinkStations all have at least one USB port and software that lets you plug a USB hard drive into them and just click "Backup" to copy everything to it. Speaking of which, it’s been a while since I backed up our files...
You can see the official LinkStation specs here:
http://www.buffalotech.com/products/network-storage/linkstation/
And the really cool firmware hacking for them can be found here:
http://www.linkstationwiki.net/index.php?title=FAQ
Like Scotty said, Kubuntu is just Ubuntu with the K Destop Environment (KDE) instead of the default Gnome setup. You can actually run both and switch between them if you want to try them both out (although it may make a mess of your system if you do that for too long). I don’t particularly like the standard KDE look and feel, but that’s all customizable anyway (as it is in Gnome).
KDE has a lot of excellent software that is well-integrated into the environment, and the upcoming KDE4 is supposed to be a major step forward. I’m happy with Gnome myself, since I use Thunderbird for email (not Evolution, the default Gnome app), Google Desktop Search (instead of the default Beagle), and Compiz Fusion for whiz-bang graphic effects. I do also run some KDE programs like K3B also, since you can usually run programs from one desktop environment in the other with no major problems.
Basically it’s just a matter of preference, so check them both out and see which one grabs you.
KDE info here:
http://www.kde.org/
Gnome info here:
http://www.gnome.org/
