EVGA offers three different coolers and three different overclock levels, and you're right, there are an incredible nine models listed at Amazon!
Here's how it breaks down:
(1) standard 9.5" blower model at reference and moderate "Superclocked" levels (not really a true Superclocked model)
(2) open air 9.5" ACX 2.0 models at reference, high "Superclocked", SSC, and FTW levels. Superclocked has a 140MHz overclock, SSC has 160MHz or so, and FTW has nearly a 200MHz factory overclock. These are boost levels, which are what count.
(3) open air 10.1" ACX 2.0+ models at SSC and FTW levels, with much better coolers and power delivery than the ACX 2.0 models. Note that the 2.0+ models require a 6-pin and 6+2-pin power connector.
Unless the 10.1" model won't fit in your case or you're on a strict budget, it's the one to get. It costs a little more for the same clockspeed, but it's worth it.