Did you use a relay harness or Just plug and play?
I am big in the Volvo C30 community and sell HID kits is why I ask . We just picked up my Wifes 328i Xdrive and she has halogens I was just going to throw a kit in.
If you guys are interested take a look at my site
MillerMotoring.com
You can read a few reviews and pictures here.
http://c30world.com/forums/showthread.php?t=21006
And lots of reviews here
http://c30world.com/forums/showthread.php?t=20922
The point I am getting to with this I am willing to much of the same. A DIY video of step by step and a before after photos and videos if there is interest.
-Joseph