Do i need xstiff or stiff flex for my irons and driver?

I went to golf galaxy and got my swing speed tested, the machine said i swing my driver at 128 mph. Now i was ripping it because i was currently in a long drive contest and i wanted to see how fast i could swing( i got up to 132 my highest) i feel on the course i would never swing this hard with a driver. so im assuming i would cut it back to maybe 115 do i still need a xstiff? As for my irons i play mizuno mp33s that are an inch short obviously i dont swing as fast as a driver so would stiff flex be better suited for me?