I think Rex has said that AquariumPlants copied some of his equipment choices. It looks like they use the same regulator and check valve, but they're using a different solenoid. AquariumPlants is using a Clippard needle valve, and I'm not clear whether Rex still includes Clippards with his regs. He doesn't sell them separately anymore except by special order. Instead he sells Fabcos and Swageloks, which are better.

I'm sure you'd be fine ordering from either.