Hi David,
I have a 160GB 5th generation ipod (
http://support.apple.com/kb/ht1353#iPod_classic_160GB) which is full to the brim with songs. Something like 200 Artists 250 Albums and a few vidoes.
My wife has a 4th gen nano and that works as well. However a friend has an earlier 2nd Gen iPod (really think and black and whist display and it will not synch properly).
I tried to find on the Volvo site which iPod firmware it supports but not luck