I would definatley say get a large one. I have an old stand alone 20 hour model, but record everything at best quality because I later extract it to archive to DVD.

It should be noted that only the Series1 Tivos are able to extract video in a reliable fashion. You just have to get a Tivonet or Turbonet card and install some 3rd party software.

That said, there is a deal I got in my mailbox today for a 80GB Series1 Stand-Alone for $199. Use coupon code GEEKTIVO to get the special price.