While notch and post sights work reasonably well with young eyes and select-fire weapons, aperture sights are usually preferred for semi-auto rifles. In the AK world, that includes Valemt, Galil and the new Russian AK12. Tech Sights and Texas Weapon Systems both make receiver cover replacements with integrated sights. Both nearly double the sight radius, making it longer than on an M4 carbine.
Some people think that better sights on AK rifles is a waste of effort. Do a simple test: if you can shoot more accurately with a red dot or a scope than with iron sights, then the stock sights are a limiting factor in accuracy.