6000k relates to the colour of the light the bulb emits, not its power... as far as i know there is only 1 type of D2R bulb, which you can buy in many different colour 'temperatures'. I have 8000k in mine for a blue tinge.
It really does sound like your ballasts mate...
I think your only options are:
1. buy some new bulbs - purely to rule out defective bulbs now... can get them for £30 delivered for a pair.
2. if that fails, either convert your lights to non-hid so that you use only regular bulbs, or buy an after market hid kit for < £50 and fit those instead.
3. if you want oem... then see if you can buy some hid ballasts from a breakers, but they wont be cheap...