How important is using a material with a high NRC rating

People are after acoustic treatment that has the highest NRC rating, usually a rating between .9 and .95. 

Sometimes the acoustic treatment that you have chosen, maybe based on esthetics, and has a lower acoustic rating then standard acoustic media. 

My advice is.. If product you have chosen has a low acoustic rating....simply apply more acoustic treatment.. It's a matter of .. If you can't get the quality.. Then go with quantity.