it doesnt look cooler, it looks ricey.
8000k would only give twice the lumens of halogen were as 4100k-5000k gives off 3 times the lumens of halogen
this is somethign i ehard, and really does fit the discription
"high kelvin rated hid bulbs are like driving in the middle of the day sun with sun glasses on, where as 4100k light is that w/out the sunglasses".
all in all its your decision,a nd its against the law to produce a blue output of light anyway.
assuming u alreasy have hid option on your bimmer, its only a matter of switching the bulbs, since the car already has everything wired to fit hid's.