I've gone through.... the following....
worst to best...
1. Luminics JDM Yellow (really, too JDM yellow, looks more neon looking)
2. Nokya Hyper Yellow/GP Thunder Golden Yellow (it's too golden, not my taste)
3. Hoen Endurance (Second to best next to Piaa)
4. Piaa Ion Yellow (My fave. I had all of the above tested on my old e60, and I ended up with the Piaa Ion, so now it's a repeat on my m3)
ohh, also, if you guys are considering doing HID, one thing I dont like about yellow-hid is that with all metal halide lamps, it requires warming up.