I don't think that I have ever looked at the sumps at the Fish Tank. You can reduce noise by using flexible tubing from HD or Lowes and by placing the return pump on a food grade silicone mat. You can get those at Bed Bath and Beyond.
That is a common design if I'm understanding what you're going to do. It makes it much easier to change filter socks. The water flows in to a small chamber that over flows on to a trey with the filter socks in it. The water flows out below the socks to the skimmer chamber. This a similar design that has a lid to prevent salt creep. http://www.bulkreefsupply.com/emerald-sump-39-trigger-systems.html You can have your drains below the water line with a conventional sock configuration. Mine are about 1" below the water line.
That's a great job! The first picture made me wonder if the return chamber was too small but it was just the angle. I almost decided to do that with a 40 breeder but I wanted to better use the space under my stand and ordered a custom sump a couple of weeks ago.
The return end was the last side I did it's a little smaller than I would have wanted I'm not sure how big of a return pump I can use. I bought a 40 breeder to use for this project but it was to big to fit under the stand so I went with this 29 gallon.
