Concerning cat5 cables, I've never seen a noticeable difference. In regards to HDMI, I would have to disagree with Kewlx25 on this one. I used to sell electronics, and there is a difference between a $5 HDMI cable and a $75 HDMI cable. Now whether or not it's worth it, that's your call. I used to put it to my customers like this. Do you really want to spend $2500 on a TV and hook it up with a $15 cable? The picture's only as good as the weakest link.