I have an XNEO-1:
It plugs directly into the NGH system where the normal AV plug goes in ...
It ouputs S-video and RGB. It has a 15 pin out, an 8 pin out, and of course the standard S-video out plug.
The picture quality of the S-video out is definitely an improvement, but I prefer Kenny-Boy's mods personally. The XNEO-1 S-video output doesn't really give you the crisp pixilated look like the RGB monitors, but it does take care of just about all the noticeable color bleeding stuff you normally see with regular AV outputs. So if you like a smoothed out and less jagged look in your games but without all the hideous color bleeding - the XNEO-1 might be what you're looking for.
To give an example, just look at Hanzo's sleeves in Sam Sho 2 with a regular AV cable, and then look at it again with the XNEO S-video hooked up to your tube. That embarrassing, girly rainbow effect on poor Hanzo's sleeve all but disappears.
Hope this helps.