in My experience the Kyroo II had the best s-video out under windows XP, Under 98/ME it was good too but XP has the clear type font that really makes a difference.
Granted though I have not used a radeon though. I do Have the Radeon 8500 and they screwed up the TV out on this card somehow, many people have the same problem with image quality. However most of these other people have had radeons and even the radeon 7500 and not had the problems the radeon 8500 has.
Forget about an nvidia card unless your going to register and buy TV tool, in order to get decent quality tv out you'll need tv tool on any nvidia card.