reshafting Ping ISI-s's

I am 26 and just started playing more often again after not having much time the past 7 years. I have had my Ping irons for 12 years since I was 14 years old, quite a bit shorter and much skinnier. At the time I was a ~14 hdcp and was hoping to play college golf someday but my increase in ability dwindled. I am now, as mentioned, 26 years old, 6'3" tall and about 190 US pounds. I hit my 4 iron just over 200 yards, 7 iron about 170ish, 9 iron just under 150 and play to about a 10.5 hdcp. I'm a pretty consistent driver, over my last 30 rounds I have put ~60% of tee shots on par 4s and 5s in the fairway (I'm a stats guy/not all with driver of course). My irons though tend to spray a bit and are hurting my score almost more then my short game. They are Regular flex JZ Cushin shafts that I KNOW are not stiff enough for me. Because of this my Dad, a ~7 hdcp and most often playing partner, thinks I should buy new irons but the money isn't that prevalent in my wallet. Ping headquarters/manufacturing is a 30 min drive from my house and offer FREE fitting and adjustment on my irons which I confirmed via phone. I figured I'd get the lie readjusted and re-shaft them myself which I have done before.

I know I am looking for either a stiff or X-stiff .355 taper tip shaft. I will base that off of Pings fitting as well as just what their swing monitor measures my swing speed at. I predict Ping will also recommend ~0.5" longer shafts but we will see. I know I will probably lose some distance but I have NO problem with this. I want the accuracy...... BADLY!

Any suggestions for shafts and their effects on my shots?

The basic Dynamic Gold of course is top on my list

Rifle?

Nippon?

FST?

If you're going to spend the money on new shafts anyway, why not just get your hands on some improved technology?  Grab some G5 irons with stiff shafts and call it a day.

for about $150 I can get these fit for me with Dynamic Gold shafts and grips of my preference. If I bought the G5's how much would they run and if I bought them used, chances they have shafts and grips I want or like?

edit***

looks like about $400 to buy them from what I'm assuming is a dealer. But I don't know if I can get the shafts fitted for me.

Wow.  I'd have expected those shafts, labor, grips, etc. to be well above $150.  I guess go for it then.

The $150 is for just shafts and grips. I have epoxy, tape and use compressed air to install grips so there is no labor or supply fee.

Global Golf has a used set of Ping G5's 3-pw great condition for 299.99, stiff flex black dot. Your ISI's have a trade in value of 100.00 bucks, not to mention alot of times they have trade in bonus deals of like 30%. So you'd have a new set of irons for 200 or less with your trade in. Id look for a new set unless you really like the ISI's. Alot of pro's still use G5's but I havent seen people still using ISI's, lol

not to mention you can find deals like this at alot of places, no just global golf. That was just me looking for 5 minutes