Component video, which is not to be confused with RGB, is actually superior to svideo and composite video connections. The color saturation is sharper and more vibrant than svideo, and like svideo, it bypasses the comb filter of the television, getting rid of dot crawl and other artifacts. This connection is the best for use with televisions that can use it, especially HDTV's, and when you're using the 16:9 mode in GT3.
These cables do not, however, split the colors up into 3 different cables, rather it splits the picture up into luminance, and the colors go over the other two cables, hence Y, Pb, Pr. If you thought GT3 looked realistic with normal cables, use these or svideo and the replays will look more realistic than any game to date. This game looks awesome on my 36 HS Sony Wega television, especially when the video is upconverted to 960i... it gets rid of all the jaggie edges on the cars, making them more realistic.
Televisions with component video will come out with more jacks in the future, mine has 2 component video and 3 svideo, which is pretty much all you need for now.
Anywho.. Oh.. try the monster cables, its definitely worth the price, the picture quality is superb.. And if you really want good sound, dont use the five cables the other guy said, use component video and the optical digital output for digital quality sound from everything including dvd.