IMO they are criminally underrated by prog fans (on this sub atleast) Godspeed You! Black Emperor, Swans and Slint are great bands that need your attention if you haven't checked them out. As for math rock I'm not as familiar with as post rock but there's a couple bands that come to mind (Giraffes? Giraffes!, Hella and Black Country New Road) I think many prog fans would enjoy those bands both genres being very progressive and have were born from prog rock but yeah thoughts?