after much research I settled on the Sicce Silent line of pumps.
They are specifically designed for either application and thus far I have 0 complaints or issues.
Having considered the heat issue and after struggling with high temps this summer, I decided that when I revamp/upgrade my saltwater, I'm going to configure the sump for both an external and submerged return pump. That way when the ambient temps start to climb I can use the pump externally and save a few degrees of heat.
The reverse is true for winter, and I will benefit from the heat generated by using it submerged.
all it will require is a bulkhead fitting and valve on the sump.