I play Ping ISI-K's 4-PW. Removed my 3I and 5W from the bag, got a Callaway 18° hybrid and an extra wedge, 52°.
I know the Pings are old, and there is new technology out there, but irons have not come as long a way as say drivers and balls, or even shoes for that matter, and if you find something that you like, I say stick with it!
Before these I had Tommy Armour 845's (oversized) and they were pretty great too. I've been fortunate in the iron department, not a whole lotta trial and error for me...