Jealous. I've been wanting to do this for years.
Go with thick acrylic for the front viewing plane to avoid condensation problems.
With the overflow, make the top of the screen below the top edge of the tank. That way when (and not if) that screen ever gets plugged, the water can over flow past the screen and into the back, rather than onto the floor.
Where is the inlet coming from back into the tank?
Check out this guy's plantonkreisel design:
http://www.biolbull.org/content/204/1/68.full.very nice in that the inlet creates a laminar flow over the outlet screen which prevents jellies from getting stuck on the screen.