I finally planted this tank and got it going. If you're interested in seeking what it looks like, check out my tank journal
I'm posting some pictures of my current project, built around a rimless 57 gallon Oceanic "Illuminata" tank. I've had enough success growing plants in a 20 high that I figured I'd try to set up a nice "show" tank for our living room.
I've always liked the look of the rimless tank/hanging fixture approach, and seeing a local club member's beautiful ADA 90p in February confirmed it. The Oceanic tank is not quite as nice as the ADA tanks, but I could get it pre-drilled through the tempered bottom. That was important to me because I wanted to hide the plumbing as much as possible.
The main DIY elements are the stand, the plumbing, and the LED fixture. I'll provide some more details about each in replies to this post.
Many thanks to all of you who helped me, either directly by providing advice in response to my questions or indirectly by posting your own experiences. I can post sketchup drawing files and more specific details if anyone wants them.