Out of curiosity, are you running an 8x or 10x bino in addition to the 15s? My current setup is a set of 10x42 Leupolds on a tripod for finding critters or shadows that look a lot like critters, then switching to the spotter to get a closer look.
My (very cheap) spotter needs an upgrade though as it doesn't give me much more detail than my (very nice) binos. I thought about getting a set of 15x binos, but the weight and $$$$$$ makes me think I'll stick with the spotters.