i would not be worried about theft - my neighborhood's way nice, i've got a security system, i've got insurance, and i really don't think any burglars are interested in moving a 300 pound object. in my experience it's usually teenagers interested in booze and easily-hockable stuff like electronics, musical instruments, and jewelry anyway.
i would be worried about condensation on the components though. it sure gets chilly around here in late october at night. wouldn't they get soaking wet inside and out once i brought them back inside and they warmed back up?