HID/Bright Headlight Conversion

Not too familiar with, but I would like to change the headlights on my 2000 golf to those really bright white/blue lights; unfortunately, im not really sure of my options. i was snooping around ebay, and i found a couple of kits. What i want to know is if i really need a conversion kit or can i just change my headlights to the more expensive halogen.

any input would be greatly appreciated.

thanks.

Jon