I found a used S&S trailer that looks like just what I want, but I've never heard of that brand.  Anyone know anything about S&S trailers? 

This is the best I can do....  http://www.ssduraline.com/

I know they build a pretty good "hot shot" flatbed trailer, know nothing about their stock and horse trailers.

S&S Trailers were built from the 70s to mid 90s in Butte, NE. I've had several. They are no longer in business but most of the parts are "off the shelf". They built stock and flatbed style trailers. Trailers were low end heavy built steel trailers that pulled like lead sleds, but, with a new paint job every 8-10 years, they would last longer than most steel trailers.