I just ordered this setup from customaquatic.com for $150 including the solenoid (you can also get it for $110 without the solenoid). I'll most likely get the 20oz (1.25#) cylinder and set it up this weekend. I'll try to post a review as soon as I can.
I also ordered the Red Sea Turbo yeast kit model for my work tank.
I'm excited about these products because they employ the powerhead diffusers. After reading Tom Barr's articles about the effectiveness of active diffusers of this type vs. slower diffusion methods such as the Hagen ladder, I was really curious to try these.