Steve: If you've time, post a couple of pics of the "long view" of your under-tank, and possibly back-of-stand set-up.
I've just set up a 50g rimless cube from Cadlights - so basically what you have except slightly shorter. Like most folks, I plugged everything in and left it on the floor beside the tank, so now I have to decide where to mount 2 vortech control units, two LED ballasts, a couple of power strips, etc...
The problem I'm facing is that I am pretty skittish about mounting the electrics inside the cabinet. There's an awful lot of high humidity and salt spray in there, and while I don't fear getting shocked (former electrician in my much younger days), I really don't want to replace a vortech control unit either b/c of salt corrosion.
After keeping "traditional" reefs for years that all had canopies, I was a bit surprised about the amount of humidity that an exposed rimless throws off. Great in the winter, not so much in the summer!