my opinion is blueline 400w ballasts with radium bulbs is one of the best sets out there for coral coloration. the 20Ks burn whiter with the 400s than with the 250s, and the intensity seems to be lower than say 400W 10Ks on other formats.
There are some goods there, they run cooler, and coral growth is moderate to good, vice screaming out of control. what you'll notice with the blueline/400W, 20K radium setup is incredible color up and a crisp white. The 400s give a little more punch, but will not fry the tank ...so no real temp control issues.
the blueline ballasts are completely cool running as well. What I've found with the Icecaps is that overtime, they tend to "fade" as if they do not hold true frequency over time, like they degrade. this is especially true with the VHO ballasts.
For the money, this is the best format. I augment mine with URI ultra-actinic VHOs. It's really quite stunning.