Don't settle on this at all
of course quality is relative to your opinion; however, with that hauppauge card and a decent vid card, which the MX should be sufficient, you should be able to tweak the vid quality to as good as or better than your cable box, or TV's internal tuner. Won't take long, just one evening a few hours and its well worth it.
A few things:
Since you mention watching a movie, I assume you are using your HTPC for DVD movies, and PVR functionality like most of us. Try adjusting your TV's contrast, brightness settings back to default, and using any sync options to see if it helps. Then adjust the contrast, brightness etc within each program, IE BTV and your DVD player. Which DVD player software do you use? DVD wise you should get really good quality as this doesn't have anything to do with the hauppauge card.
If you need a hand tweaking it let me know and I can give you my IM and help you out if I can.