I just picked up an HDTV box. I currently have DAC-100. I don't think the firewire port on my cable box works, so it's composite or hdmi for me. What would be a similar device I could use for grabbing and then encoding HD?

On a slightly-related note: One thing I'm considering doing is setting up something like a Myth box and getting an HD capture card, but I don't think I can get all the hd or sports channels, so it might not be worth it. But it would be nice if I could, because then I can just slice up anything I record. Am I wrong here?

I'm not dabbling in HDTV yet. I really have no idea.

What I can say is I doubt your DAC-100 will be of any use, without downconverting the HD. For HD captures, you'd want to grab a special HD capture card. I think both Hauppage and ATI have some good selections in that area.