the great thing about having an iPod and a Mac is that you can pay a rather low fee and get all kinds of goodness from audible.com such as mostly anything from NPR/PRI right onto your iPod. you can even get the NYT every morning read for you. it is an abridged version i gather but that is still rather swell. so i would go for the 40GB one keeping in mind that you may be archiving oodles of NPR. that is what i would do if i had a mac and etc.