Re: I currently use this TV Tuner on my 19"LCD for reg cable via Coax..Digital box or
It appears that these devices aren't actually the tuner. They take the signal from a tuner and convert that signal to one your monitor can display. With that in mind, the first device you mentioned doesn't have component jacks. So I doubt if you could get true HD out of it. It's possible to convert component to composite or s-video, but you lose quality that way and it's not true HD.
The links in your 2nd post didn't work.