Get yourself professionally assessed, and be very honest with them as to your perception of the club feel as you swing different stiffness shafts. The vast majority of non pro players consistently err on the side of having far too stiff a shaft on their clubs.
I consistently get timed between 100 and 103 mph swinging a 5 iron and that's just my regular full swing, it's not like I'm trying to mash it just for test purposes. I play regular stiffness Dynamic Gold SL R300 steel shafts on my irons with no problems of ball control at all. Most amateurs do not swing with a club speed lots faster than mine, yet I see loads of guys playing stiff or even extra stiff shafts who have swing speeds that in no way, shape or form justify that stiffness. All you accomplish with the over the top stiffness is to kill the feel of the club and your distance. JMHO.