This is the best thread I have seen on the subject in the last year and I have copied to the two posts from it that were the most informative IMHO. Everyone loves the choice they make so you tend to get a lot of testimonials. What makes one persons testimonial better than anothers? Use this information to make your own decision.
http://www.bimmer.info/forum/showthread.php?t=21511

Originally Posted by
joshua43214
3 pages and no one has answered your question.
I shot over to the sylvania webpage to have a look.
These are the standard buld line
bulb kelvin lumens msrp
9005 3200 1700 $16.00
6006 3200 1000 $16.00
The silverstar line
Bulb kelvin lumens msrp
9005 4000 1700 $50.00
9006 4000 1000 $50.00
Philips 4100k(HID)
kelvin lumens
4100 3200
As you can see, the 9005 bulb provides 70% more light for the same cost, upgrading to the silverstar provides a 25% increase in kelvin for a 300% increase in cost.
Upgrading to HID provides a very small improvement in color over the premium bulb, but almost 2 times the lumens of the 9005 and over 3 times that of the 9006.
there are HID lights that go all the way up to 7000k.
My opinion for what its worth, doing the mod to the 9005 bulb is worth the effort. upgrading to Silverstars approachs diminishing returns when you consider it is $100.00 for both headlamps. Upgrading to HID is worth the money if you have it to spend, other wise use the Ultravision(30% more lumens than standard. $25.00) modified 9005.

Originally Posted by
joshua43214
Kelvin relates to the color of the light.
Lumens relates to the amount of light output.
The higher the kelvin, the more blue and less red the light is. the lower the kelvin, the higher the red and the lower the blue.
daylight is aprox 5000kelvin
white light(studio reference) is 3200k
incadescent household bulbs are about 2800kelvin
kelvin has nothing to do with how much light is emited or how bright it is. It does however affect the eyes ability to pick out detail. Our eyes work best in daylight, so we will see better with 5000k bulbs even if there is no gain in lumens.
You have all heard of infra-red and ultra-violet light?
Dinan chip, Bilstein sports w H&R, RD sways, RD strut brace, 750 bushings, Zimmermans/MetalMasters, O.E. M Pars, Eisenmann muffler