I would agree that a 16+ with Recaros is worth getting, and I would get a new car, it's nice to have a car no one else has (possibly badly) driven. Sync 3 is a definite improvement starting with the 16's, and I say this even as mine is right now in the shop getting a new APIM (Sync 3 module) on warranty after it wouldn't update, and Ford diagnosed a bad APIM. I may feel differently if this repair doesn't help.
The stiffer RMM is nice, I haven't felt the need for an aftermarket one, and it's definitely nice to have one with the new head design that will hopefully avoid the problem of burning up coolant that led to the recall on earlier ones.
I also like the Recaros, they are quite tight when new, even for me at 6' and 165 lb., but they do relax some with use and are really helpful when whipping this agile little beast around turns. They also upscale a pretty basic interior, giving a little more of an enthusiast feel. The FiST is the cheapest car you can get with factory Recaros.