I would post your build thread in the Setup and Filtration forum since it sounds as if most of your project will be having the tank built professionally, you already have the Eheim filters and will eventually be asking about substrate, heater(s), other potential equipment, water movement, lighting, etc.
Just pick an appropriate thread title, add dialogue and pics as the thread progresses with your updates. If you are not positive on what fish or tank mates you will be stocking, just title the thread as something like My (insert tank size) Tank build or something similar.
Some people start out with a general idea of which fish they want to keep and then change their minds down the road but a general build and set up thread is nice to see.