The resolution is important. If it's SD (480), you won't likely see any improvement beyond what you're getting on S-Video.

If it's a 720p, you should be able to use the component inputs for a real improvement.

What does your video card output? On first glance, I'd think that a new video card would be a much better choice than either of those converters. The modest Gigabyte card I have comes with an adapter to go from its DVI output to component.

If your TV only has S-Video and composite inputs, you're screwed.

bibere usque ad hilaritatem