It is better if you pick the higher kelvin rate.
I also use osram MH bulb, 150W daylight. There is no rating on the package but the official local distributor shows me the catalouge and it is rated at 5600K.
This kind of bulb, like all MH will degenerate its kelvin rating over time. Mine is slightly yellow right now from its whitish original. I got mine from the local osram dealer for US$10 each (original but cheap since it is usually mass-used in lighting billboards and such).
Do combine it with 10,000K CF (even though the MH will overshadow everything with yellow hue) to make it look a bit nicer as well as making the light more even.
If you ask me if it works, yes it does to a certain extent.