Opinions on 20K SE metal halide bulbs

[Stones]

The radium was the main bulb I was considering however I've read several reviews that said it didn't emit a real nice purplish colour and was actually closer to a 14K bulb than a 20K bulb. The nice thing about the Radiums is that they were meant to run on a HQI ballast.

I'm also a big fan of XM bulbs but have never tried them on a HQI ballast. Has anyone ever used the 20K XM's on a HQI before?

The last bulb I was considering was the 20K Sun Aquatics, as a review I read said that it had a deeper purple colour than did the Radium 20K. I have used their 10K in the past on my HQI ballast and it ran way too yellow for my liking, but I'm unfamiliar with their 20K bulbs.