^ Ah, great, now we're on the same page.
So my question now becomes centered on your other three pistols - the M&P9 Shield, G19, and Rock Island CS. What is consistent about those other three, sight-wise, that allows you to be more precise/accurate, under the conditions/stipulations you're putting on the criteria?
It seems that you definitely have more than enough experience to know, and I would bet that, with your experience, you're more than likely right-on about your need for more daylight around the front post....
Do you have the specs of the sights that you are running, now, on your other three guns? If you have their physical measurements, you can then work from the sight radius to figure out the approximate ratio you'd be looking at, with the sight radius of your XD, and then start looking at aftermarket sights/sight sets from there.
Otherwise, my initial request to you stands - please understand that my intent to funnel you towards a beginner-level class was not meant to be a slight towards you: rather, that it's simply the places where you are most likely to see the greatest variety in firearms/sights gathered in one place.
Your most likely place to be able to sample from a wide range of what's available.
Alternatively, after you get some measurements, I'd recommend that you speak to an XD-platform sights specialist like
ajamesp51, the proprietor of XDman.com . It's possible that he could give you some recommendations based off of your personal preferences and observations.
Finally....
You mentioned in a previous post that you liked to see the rear sights.
With your new information, I'm wondering if perhaps you "look/see" in the way Frank Proctor does.
Given that possibility, I wonder if his WOTG Y-Notch Sights can be adapted/modified for use on an XD? And, of course, if it would strike the right balance for you, given your visual preferences for the sight package.