Peter White Bicycles is a good source of information. It takes a while to digest but there's lots of info there. They import a lot of lighting products. In my case, I figured out what I wanted, went to my LBS, they suggested some tweaks, then ordered the parts from Peter White. They charged me the same prices shown on Peter White's web site (apparently he has lower pricing when selling to other shops). That was several years ago and the system is still working great.

Even if you don't buy from them, their web site has a ton of info.