Looking into new spotting scope. Have a close friend with Leupold Goldring 12x40x60 and have always been dissapointed at the upper power levels. It blurs to the point that it is almost unsuable and has even been sent in for warranty work. I'm definitely interested in the Vortex. How much of a difference is there between the Viper and Razor? Does clarity become a problem at the upper power levels?