The shafts you have now are extremely soft compared to any of those. Stiff would be like a regular or senior + flex when compared to tour weight shafts, since they're only 95 grams and designed by TM to go into their distance irons.
KBS would be my recommendation; they are only 120g in stiff, should be a mid flight compared to the others and feel nice and smooth. Maybe consider the S+ or soft/hard stepping, personally I love the brand and would recommend them.
Dynamic Gold is worth trying, but it will be a big difference because they're 130 grams. I would hesitate to go that heavy unless you try them first, but flex wise they should work OK. Project X are considered harsh by some, and rifle are not shown much love.
As I read your profile though...If you actually hit that 8 degree R11 with a Fujikura Motore F1 75x, you're either a vain individual who's hitting a lot of worm burners or you have quite decent speed. If you actually like or were fitted to that shaft, then go right ahead and try the different 130g X flex shafts. Many players do prefer softer iron shafts, but if you're playing such a low lofted driver with a legitimate X shaft like the fuji then at least try X. I'm honestly kinda confused why you're only considering S flex in your irons.
Remember that Project X steel will play about 5.5= DG S300 and 6.5= DGX100, while the KBS will be about the same as the dynamic gold flex wise. The Project X 6.5 is a lot more stiff than anything else on the list. However while DG are all the same weight, KBS and PX are progressively heavier.
Personally I use C tapers in X flex soft stepped once, so they're 130 grams and tip stable but play similar to a typical X flex shaft. C tapers are really low spin/launch so they play half a flex stiff normally.