Hello, HDM25. I've been a HP afficianado for 30 years now. The first custom work I had done on a '71 HP was the instalation of S&W adjustable revolver sights as the adj sights on the Browning would not hold zero and were too high. I still have and use that pistol.
It also has a slightly extended custom thumb safety.
As the HP is my favorite pistol, like many others, I began to think that I HAD to have this or that custom change made on this or that HP and paid a local artisan to do the work. I usually wound up NOT keeping that pistol
For me, I finally learned that the "right" thing to do was as little as necessary to make the piece more "shootable."
Recently, I had Novak fixed sights put on a MkIII, actually 2 MkIIIs. They look great and I really like them, but if you ask me if they do anything that the original fixed sights that came on the pistol do not, the answer is "no." I like the way they look and they do make the pistols more pleasing to the eye in my view, but in practical terms, nothing was truly gained. (By the way, I am not saying that one shouldn't have a piece customized for "looks." Pride of ownership is important, too.)
With current MkIIIs, all I "need" to do is bob the hammer spur a bit and I remove the ambi thumb safety on the right side of the pistol as it gets in my way. IF a trigger job's needed, one is done. I remove the magazine disconnect for a better trigger pull and because I hate the things. I replace the nylon stocks that come standard as they don't feel comfortable to me.
I've seen and handled Novak HPs. They truly are works of art and are practical in execution. Essentially, what you're getting is better trigger, better-looking sights, beautiful finish, and (possibly) a more reliable pistol that will have more "practical" accuracy because it's tuned and more comfortable.
Only you can decide if it's worth it.
Having said all that, I suspect that you could take a fine Novak gun and shoot it for group against a much less "refined" MkIII and note no real difference. The same would hold true for "speed work."
I pitted my custom HPs against my HPs that merely had the factory MkIII sights and the minor changes I mentioned above. I could tell no difference.
$1600 is a tidy sum, but you can make more if that's what it'll take to get the gun of your dreams.
Best.