You should be able to build the same machine for no more than $1,500. That's why kastriot feels as though they could have included Windows Pro.
Here's a similarly spec'd iBuyPower on Amazon fro $1,449.
I would have mounted it with the pump on the top. That way your text isn't upside down and the tubing isn't stretched. I know it's recommended to place the pump low in your loop so that air doesn't get trapped in it. However, given it's a closed loop, I doubt that air is an issue.