Just a word of caution to those of you looking to 'upgrade' to these xenon bulbs. There are sellers on ebay who are offering versions of these bulbs and quoting them as 'an upgrade giving brilliant blue or white light'. Be careful - some of these are just cheap chinese rubbish that are not worth buying - the light emitted is greyish and very poorly defined, and they are so poorly made that your headlamp alignment may be affected too. In my experience they were dangerous to drive by at night, giving me a few heart stopping moments due to not being able to see clearly enough to drive safely with these bulbs fitted.
Basically, you get what you pay for, so if you want to get bargain bucket bulbs don't expect brilliant performance. Ignore the false economy, and go for a recognised make such as Philips (eg Vision Plus) or Osram (I am using Silverstars at the moment, which are excellent), you may have to spend a little more but believe me, it is well worth it in the long run. Don't be tempted to get the higher wattage (100w) bulbs either - you may have problems with overloading vehicle wiring circuits, or even melting your plastic reflectors! The 55w bulbs are what your car is designed to run, so stick with these and you won't go wrong.