Wow, beautiful setup! Congratulations, and thanks for the pics!
Now, about that hum, does your setup include some sort of set-top box for cable TV? Often, the source of the hum is the grounding of the outdoor portion of the cable TV setup. Some have fixed it by hard-wiring that ground all the way to the ground stake used by the incoming electrical service, while others have needed to install an isolator indoors, inline with the coax cable connecting the outdoor portion to the set-top box.
See for example this thread:http://www.avsforum.com/t/1462679/integrating-sub-lots-of-questions-gain-noise-crossover-etc
If you have such a setup, you can evaluate the hum by disconnecting the coax cable that runs into your set-top box from outdoors, being sure the system is turned off when you do so. If the hum is gone after you turn the system back on, that's your culprit.