Just a link but this is a really nice comparison.Worth checking out if your in the market for shocks.
http://www.yfzcentral.com/invision/index.p...showtopic=37883
Shock Comparison (unbiased)
I guess I never counted an SSD spring as a one of the rated springs. I've always heard of a triple rate shock with SSD, hence three wieghing springs and a SSD spring on the top. But I do see what you mean about a quad rate shock and TCS not having one. If you want to count them that way, I didnt know they put SSD on a triple rate either.