Hi,
I hope I am able to address your doubts.
1. If a channel transmits a picture in HDTV quality and you don't own one, you won't simply notice any difference, you might observe the image getting a bit sharper and clearer but the smudge would still be there.
2. Most of the better channel transmit high quality pictures, in India Sony and Star do for sure.
3. DVD and HDTV is a completely different concept. DVD = Digital Video Disk, or a storage form to save your softwares (including images and videos)
HDTV = High Definition Television. I assume you understand the difference between a television and a disk?