S-video question for consoles

[Master LL]

I have a Gamecube and Playstation 2.

Soon, I'll be getting my tv tuner card for my PC and am planning to play with my console on it (not to mention record videos from gaming and watch tv.... plus watch movies with my dvd player [PS2]).

I was wondering if I should just use the default "audio Left/right" and "video" to view my movies and play games.... or should I use "S-video" instead of "video" since I know it's higher quality and such.

The reason why I asked is because I dont know what I should buy if I plan to use the S-video connector (since obviously the GC and PS2 doesn't come with one).

Should I just buy the s-video connector seperately for each console or is it possible to use an "S-video adaptor" or if so I can plug the "video (yellow plug) into the S-video adaptor for it to work (if there is such a thing).

Any advices is welcomed. Hope you understand in despise my horrible explaination.