If you're using a Radium, don't use an e-ballast, stick to an HQI. HQI ballasts have ignitors that assist the ballast in firing the bulb, and even on SE radiums, they need that extra boost to get them fired right. If you don't run them on an HQI, they'll not have the proper output or lifespan. As far as the manufacturer, as PSU pointed out earlier, I'm not entirely sure that it matters. As long as it's put together properly, any ballast should produce close to the same results, and I'm sure if you tested each brand, you'd find variance model to model that usually made each ballast intersect the output of the others. I'm sure there is actual research out there on this topic, so you may want to look that up if you're serious about finding the ballast, but anything else you get on this site is going to be strictly anecdotal...(i.e. I use this and get great results, I switched to this and my colors exploded, etc. etc.)