What are you switching from? I liked my Ushio 10K, but found it a bit yellow. It was very brite and has a very High par. I switched to an XM 20k, which is very blue, but still nice. Much lower par. I since have heard that the XM 10k's are a really cool compermise. I think these will be my next bulbs.
I don't know your setup, but if its a three bulb setup, I would go 1 10K Ushio in the center and 2 20K's on the ends. I have a two bulb setup but would die for a three.