I have built a couple and finally gave up and bought a Miller coolmate 1 because it's fan was quieter. My shop built ones cooled well but after a few hours of the pump grinding away it would just make you mad. I figured the shop hours and the cost of the parts of my shop built tank just didn't save me much over the cost of the miller which ran about $500 when i bought it. If I had city water to my shop I would have hooked up a solenoid to the water line and used the city water which then can be recycled to the garden or just down the drain, and doesn't make any noise. The coolmate fits well under my Dynasty 200 and has been trouble free.
That being said your unit looks very well engineered and built- good job!