the 3i vs. gap wedge discussion is always fun.  the 3i is a blunt force weapon that usually brings every hazard on a hole in play when you're a 15 hpc.  on the other hand, the gap wedge can be quite the opposite when mastered, and much easier to master. if we assume you don't have any problems reaching par 4's in regulation on the courses you play, then most assuredly you'd get more use from a gap wedge over a 3i. and if you intend to mostly hit full shots with your gap wedge the case for matching the gap wedge to your iron set, including the shaft  --rather than matching the 51*'s shaft to your wedges -to me, is a strong one.  simply stated, the gap wedge in my view is more useful.  

 

 

 

 

 

 

I would get the 51, personally. The 3 iron is not really added value, IMHO and most people have a hard time hitting it. You're going to save more strokes with your short game than your 3 iron. A 51* wedge is a very handy pitching and chipping club. You can also use a 51 for long bunker shots. My wedge setup is 50-08 (bent to 51), 54-11 (bent to 55), and 62-07. This is for a wide variety of conditions. I can hit a long bunker shot with the 50 and can hit a pitch shot off a hardpan lie with the 54. The 62 works in soft sand or hard, hard lies or soft (I got it primarily because it overcame the limitations of the 60-07 and 64-07). I would leave your 54-60 setup alone. 54 covers a majority of shots under 50 yards. The 60-07 works nicely in hard sand, although not so well in soft sand (which you should be using the 54 anyway with the face way open). 52-58 would not really be an adequate wedge setup (some may differ with me). The standard 52* deg gap wedge doesn't have enough bounce for long bunker shots (50-08 bent to 52 would give enough). You would have to make your 58 your primary bunker club so 58-12 might be the choice; however, it doesn't quite have the fortitude for medium to long bunker shots in soft sand and too much bounce for hard sand or tight lies (you would have to play a digging style shot). I had 51 (Golfsmith P2 GW), 258-12 Vokey and Alien 64-05 between 2007 and 2009. The 64 worked in small bunkers with hard sand but was inadequate for larger bunkers.