If I remember correctly, OEM HID's don't go higher than 4300K. Weather it's BMW, Honda, Mercedes, ect... DOT doesn't allow more than 4300K (I think)
HID's actually use less watts than halogens. Halogens=55w and the more common HID kits=35w. I wouldn't worry too much about the electrical system, they re pretty decent and if anything actually goes wrong, that's what your car has fuses for. If you want another layer of protection, you also add what's called a Relay Harness.
12000K on my Mazda...
Obviously you can tell which is the HID and which is the stock halogen bulb.
Just remember the higher temp you go, the less usable light you lose. For best visability you want between 4300K-6000K. I went with the 12000K for pure color/looks. The visabilty isn't too bad, but it'll be better if I went down in temp.