How will switching to graphite shafts affect my game?

I have an issue with slicing. To cure the issue I went ahead and eliminated woods from my game (including the driver), because I feel the flat face of the irons are the main reason why I don't slice them. I have Tommy Armour 845 Stiff Steel shafts now. But I've recently tweaked my right knee (I'm a righty golfer) and have had to cut down the speed of my swing to eliminate wrenching it on the follow-through. So I've recently decided to switch to graphite shafts. I currently hit my long irons very consistently and what I feel is pretty far (3 is at 210; 4 is 195; 5 is 185). Is it likely that I will lose/gain power and/or lose/gain accuracy with these new shafts.