I use mono pole for my surrounds, but the bipole work better for some setups, my mothers living room gave better effects with the bipoles, but her's where at ear level and her seating was 90* {L shaped}, my surrounds are mono pole but they are mounted 3 ft above the lp and at each end of the single straight couch, so when I tried bi, di, and omni poles the monos sounded the best. Obviously if you have the means to try a few different types that would be your best bet.... Everyone prefers something different, my uncle swears by Omni pole {he is a mirage junkie} and to me his surrounds sound too "echo-E" like they fire late and muffled, but I use nano-sats in my bedroom for surrounds and they sound great.... Testing is the best method to choose...