Hi Gary,
When I first set up my Seleco I connected RGB, S-Video and Composite because I had no idea which would be better. I found the RGB to be better until I replaced the S-Video cable with a good quality one as I had been using a home made one. I couldn't tell the difference between RGB and S-Video but composite was not very good at all. I did the focus and convergence three more times over the next 2 years and still couldn't see a difference between the two.
Since then I have moved house and have only S-Video connected and a larger screen.
I may not be as discerning or as critical as you though. I also wear contact lenses that, whilst they give me 20/20 vision, do not really fully correct my eyesight.
My amp only switches composite and S-Video too.
I have recently been thinking of buying a DLP but every time I use the Seleco I am so engulfed in the experience I wonder why I would consider such a device.