Based on tests and the hue not being too blue, I picked the aforementioned Osram Night Breaker Unlimited D1S bulbs. Before them, my car had Philips XenStarts, but I'm not sure how old they were. Still, here's a comparison I made. Right headlight is pointing slightly downwards on the Osram photos, but the difference in output is obvious; with identical camera settings the ground is overexposed.

To match the 4350K Night Breakers, I have 4200K Osram halogens in fog lights (64211CBI) and cornering lights (64212CBI), as well as 4000K Osram LEDs in side markers and parking lights (2850WW-02B).