+1 for the combat sights with fixed, low power magnification; Elcan and ACOG make some great ones.
I have no experience with the Sig or Primary Arms prisms, I am assuming their quality is similar to the Vortex Spitfire or the Burris AR332. I've heard that some of the budget prism optics from various manufacturers are literally made by the same factory. It seems plausible, given how close the form factor is between models.
Steiner and Hensoldt each make fixed power combat sights too, I looked into them while shopping around. The price points seem to fall between the ACOG and budget offerings.
My best prism optic has to be the Kahles k4i, it's just pure clarity and the eye relief is very generous