the philips x-treme bulbs are good-i got a set of e bay £20 for twohttp://www.powerbulbs.com/product_detail.asp?prod=81
I have used Osram NB's and philips x-treme. The philips were a better light but one went within 3 months of it going in. (that was in the summer so they were hardly used.) I dont know if this is common or a one off in my case. They both get rid of the yellow and produce a nice white light. I would go for the philips. They are better than stock but do not make masses of difference in light output.The main difference is a whiter light which is what I wanted. I have now purchased some vw xenon headlights which is the only way to dramatically improve light out and visibility.
It gets rid off all the yellow mate. Your left with a crystal white light. They also improve visibility slightly. If you do go for the philips I would defiantly recommend changing the sidelights as well because the yellow of the sidelight looks rubbish next to the bright white!You wont be disapointed with them if you want to remove the yellow from the standard ones.