I have run for some time 3 blue+ and 1 sun on my Icecap (run 8 hours) and had 2 more blue+ on a Triad (run 12 hours). This is similar to the Radium look, but brighter and whiter (and hard to take a photo of - comes out more blue than meets the eye, I will have to do some photoshop work to adjust). Even with only one 'white' bulb in the mix, still whiter than you would think (whiter than a Radium MH).
I recently changed to 3 blue+ and actinic on the Icecap run (12 hours), and 1 sun and 1 aquablue on the Triad (run 6 hours). I like this much better. The 3 blue+ and actinic look better than a Radium IMO, and the two 'white' bulbs on in the middle of the day look whiter than the look I had before. Even though you would think 3 blue+ and an actinic would be only blue, these bulbs produce some light in the rest of the spectrum, so when you have a bunch of blue bulbs , all overdriven, there are enough of the other wavelengths to make my yellows and reds look nice too.
I am getting a couple of the superblue bulbs Grim spoke of and will be taking photos before and after the change. To be continued.