5 1 tera
byte drives on a simple freeNAS
http://www.freenas.org/ software raided should cover that

, you might need to add in a few more MultiWAN connections though to get that without any VM STB kicking in and slowing you down.
try using "ISCSI" on there for your remote NAS connected drives on windows , works a treat over cheap RTL 1000Mbit/gig ethernet LAN cards.
althought theres also the alt and darknet (darknet were only your community LAN users can access your internal linux usenet collections etc

) so you might need a second or 3rd FreeNAS box for that.....
well, you can always just be selective in your newsgroup selections and bring that 4.45TB/day dataflow down a little