While I haven't used this, it does seem like a pretty good deal just remember you have other items to by that will add around $100,00 or more depending on what you want.
I built this reactor myself from these same plans and it has worked great. My calcium level stays between 400 - 450. I use KNOP, KORALlith for my media as it is 99% pure, and contains no phosphates. It can be purchased at, http://www.petwarehouse.com/
I have a dual chamber reactor by myreef (Andy). It works great! Go with the dual chamber unit. I think you will more happy (although I have nothing to base that on).
I think the dual chamber is basically for larger gallon aquarium and to remove more CO2 before it goes in the fish tank. I personally own on of Andy's 6" dual chamber calcium reactors and have been happy so far. For the price you cannot beat it. I also suggest the dual chamber, not that much more money and I would also go with the 6" tubes over the 4" tubes. You will also need a CO2 tank and pumps and regulator, talk to Andy and he will tell you were to get them. You can see the 6" dual setup on my web site.