Hi,
We carry the Sunlight Supply Galaxy select-a-watt ballast which is virtually the same thing as the Lumatek, with a different paint job and brand name. You're essentially getting the same options, wether you want to call it "dimmable", or "select-a-watt".
Having said that, I personally do not recommend dimming halides. To get the maximum longevity (color spectrum) out of the arc tube, it needs to burn at the appropriate temperature. This means that you need the correct voltage supplied to the lamp. When the voltage is lowered, then the resistors life will be shortened, and the arc tube burns more dim, in the end greatly decreasing overall lamp life and spectral life.
In my opinion, the Lumatek and select-a-watt Galaxy are excellent choices, and very versatile if switching from different wattages or lamps. I personally do not like them to be used as a "dimming" ballast though, and in doing so will void any warranty on the lamp being used.