If you read the threads, many of the commercial regulators are single stage, even the carbon doser. The way I understand it is, a dual stage reg will prevent end of the tank dump. I have stayed away from a Ca reactor and wanted one for years. You hear the stories and read the reviews of people not being able keep them dialed in, or the media melting. Dosers are another story, but how many people have wiped out a tank with one. If I am going to really on a piece of equipment, I want to make sure it is going to work properly.
I was going to buy a Carbon Doser until I read this thread. Picked up a dual stage reg for 35, hoke metering valve for 25, burkert solenoid for 48. Had to replace a gauge which was a few bucks at local welding shop. Even if it costs another 50 to buy the rest of the fittings I am well below the price of a Carbon Doser. I can even show it off, maybe the centerpiece at next Thanksgiving dinner.
Also grabbed a masterflex for 125, and another 40 for the tubing. Seems to work fine, but probably won't when I got to hook it up