Box looks solid. I would have put a few strap braces across the bottom panel though as it's pretty large and will probably flex some which you won't be able to see, but could hurt output.
FYI on Gorilla glue. I recently tore apart an 18cube box that was 1 1/2" thick walls, braced like crazy, etc... I used PLENTY of glue, but when I tore the box apart it only stuck in random places, and not very many at that. Seems like the screws/caulk held it together. I had also read that test, so figured tearing this box apart would let me see first hand how it did, and it SUCKED!!!!
I'm sure your box will be fine though, as mine never had any issues.