The best irons for pure performance (if swing meter speed is no problem) IMO are the lvl 90 TM irons you covet, but they will make the starter balls' meters "fly"!
You indicate that it would be a problem, so I recommend that you work your way into better golf balls for better scores (WGT's brainchild and revenue provider).
What makes these irons better is their higher trajectory whereby you can expect to shoot longer with less "after roll", but the balls make all the difference in the world!
I suggest you try medium quality balls with good "feel" ratings, such as the (2 1/2 ball) GI 3D and the GI 3S (94 cr and 99 cr respectively). If you need free credits and do not wish to fill out surveys, there are videos to watch. They eat up time but deliver points consistently whereas the rotating view panels are for "views" and take longer to deliver increments of 75 Credits (for 100 views: the best ratio).
The reason I suggested these two balls is that they play remarkably close to the number and you can play the full reverse spin on 3-pw iron approaches without drawing the ball back off the green. (In rare heavy face wind, you might move the backspin dot closer to neutral so the ball doesn't ride up into the wind and drop too short, especially if clearing water or bunkers.)
On Beth 5, don't aim over the bunker unless you fell POSITIVE that you will clear it! The front PIN position is a sucker one because virtually nothing on shot two that reaches the green will hold it. Practice your flop and short max loft wedges after overshooting green in 2 if going for back PIN location, but that would be for eagle!
Beth 7 is an SOB for anyone, requiring super precision on front right PIN and exacting aim for the longer left back PIN. Learn your after roll number for this shot!
Beth 9, like 5, holds the same rule - don't play over that corner dogleg bunker unless you are positive that you can clear it on the fly! On the left PIN approach, putts are better than chips, so make sure to reach green! On the right PIN position, it looks tougher than it plays and I often take 2-3 yds off my "number" successfully. I have tapped that flagstick often, dropping two for eagle.
Bethpage is a perfect testing ground for these new irons!
One last note of warning about #9 - when trying to clear that dogleg, even if you have enough driver, an early hit (meaning hook) can land you in some nasty 80-90 rough, that risk is not worth the reward.
Good luck!