Part of me just wants to use herpstat intro+'s as the cost is actually slightly less and they are already setup for a panel mount, but they are lacking a few features that I like in the 4. I'm by no means going to be building this entire system all at once. Right now I have 6 AP T8's and a few other size AP cages but I want to have a plan in place for expansion.
The computer rack idea is a good one. I've opened up a herpstat 4 and there is enough room inside for the screws/nuts that would be required to attach them to a rail. I have also considered using hot glue, but I want this to be as easy to maintain as possible so I would like to avoid things like that.