Media storage for iTunes buys and archiving material from Sky PVR

[SilentJOB]

Hello,
I would to like archive iTunes buys and shows recorded from my Sky HD box.
I use a neuros osd with a lacie USB key to copy from the Sky box and convert the shows using iTunes to save to an Apple TV 160gb box. This is ok for shorter shows, but tiresome for material longer than 45 minutes.

I'd like to boost the storage capacity of the Apple TV 160gb.
What's the best way to do this?
Also, is it possible to digitally save the recordings from my Sky box directly to some sort of Network Attached Storage device?
Ideally I would like an reliable, simple, upgradable solution that works with ITunes and Windows. Does such a device exist?

Thanks for reading and thanks in advance for your help.