Ok, i'll try to go back to basics and explain in everything in broad detail
Firstly, there are two types of headlight housings that cars use - i) reflectors and ii) projectors. Normally, reflectors use halogen bulbs and projectors use HID bulbs. You should only use HID bulbs for housings that have been designed specifically for them. That's why it's not good to put HIDs into reflectors because they are normally designed for halogen bulbs, not HID bulbs. A retrofit is where you get the projector that has been designed for HIDs and you put them into a reflector housing. That way you can actually properly use HIDs.
Secondly, the colour of light is based on the kelvin temperature (K); 4300k, 5000k, 6000k etc. What you normally see in cars with yellow-ish lights is about 3400k. As you go higher and higher, the light becomes whiter and whiter and then more blue. 4100/4300k is what you normally see in cars with factory HIDs - it's white with a slight tinge of yellow. 5000k is pure white, 6000k has a slight blue tinge and then it gets more blue as you go up. It's important to note that as you go higher up on the kelvin temperature, the actual output of light decreases. 4100/4300k is pretty much ideal as it produces the most output of light. Above that, the amount of light put out decreases. So no, 6000k is not the best for light coverage. Sometimes you see cars on the road with really blue lights - you may think it's bright and have the misconception that it's putting out a lot of light but infact it's only because the lights are producing a lot of glare.
Thirdly, HIDs do produce more light than halogens but you shouldn't really be using HID bulbs unless your headlights are designed to handle them properly. Hence, in your case it's better to stick with halogen bulbs. If you want to get that white colour then you should be getting halogen bulbs like these -
http://www.powerbulbs.com/product_detail.asp?prod=94
I tried to explain it as simply as I can, I hope it cleared things up a bit!