let me list out everything thats wrong with this quite simply. please dont take it personally. i am only trying to answer your original question
1. Kelvin does NOT mean brightness. optimal "lumens" occur at around 4300k.
2. 6000k temperature lights will decrease brightness minimally, ballpark/out of my *** % would be decrease lumens by 10%
3. 10000k temperature lights will effectively kill your lumen output by (again ballpark/out of my *** %) 40%
4. Stock bulbs are PHILIPS, 4300k. These will be the absolute brightest bulbs you can get
5. JW motorsports probably sold you cheapshit chinese HID bulbs for 20-40 dollars. with HID's, you get what you pay for
6. the blue-est, brightest bulbs you can buy are
these - Philips 66240 CBI. they are rated at 5000k and will probably last you the life of your car.
7. the reason your friend's bulbs probably look brighter are because they're putting HID's in non HID projectors. reflectors and halogen projectors focus hotspots in front of your car. HID projectors project a wide, evenly distributed, and farther reaching light