JDM headlamps are designed for driving on the left side of the road and have the beam aimed to the left (compared to headlamps that are designed for driving on the right side.) So, if you drive on the right and use JDMs with halogen bulbs, you are already glaring other drivers. With HID conversions, you will definitely be dangerous to other drivers.
If you are going to use the projector from Audi A6 then it should fit with a bit of work. But maybe use some smaller projectors.
If you are thinking of only using the HID bulb and plug it into your stock housing then it really doesn't matter which car it came from. The light output isn't going to be any good tho.