I got my NECG sight because my 458 shot way too high with the standard open sights. I didn't have to replace the front sight at the same time either - mind you it will still shoot high with projectiles lighter than 400gn but I could file a bit off the bottom of the underside of post to gain more height adjustment (the post base hits the top of the receiver before it runs out of screw adjustment).

400 and 500gns are my standard loads and unmodified NECG will accomodate the adjustments to suit both with the standard front sight (which is the right size and colour I reckon).

Initially I was going to try a taller front sight but the Recknagel units are about the same price as the NECG and the later is fully adjustable, and the AUD is very good at the moment so the NECG it was. I'm going to buy another for my 375.