Bruce,
Hi there. My understanding is that, all else being equal, the quality of RGB tends to fall between component and S-video. This depends greatly on the cabling though, eg top quality S-vid cable will outperform average RGB cable. This means that:
a) You would need top-line scart cable like QED Squart. (£50 British money, so maybe $50-70.)
b) You need to be sure that the converter uses quality materials hence retaining the intended detail, colour definition etc.
c) As RGB is (and I use the word loosely) better than S-video, you would achieve little converting from S-vid.
d) Theoretically, you would see an improvement converting from component to RGB. How significant, and whether it's worth the cash, is something for you to decide. Maybe you've a friendly retailer who will allow you to loan the bits for a trial? Good luck whatever you choose.

Dan.