4300K is the brightest you can buy period. All OEM manufactuers use that kelvin rating when they add HID's to a car. The blue tint is usually from the way the reflector/projector is designed on OEM equipped HID's.
Now for a car that isn't HID equipped from factory, the reason why there is jumps in kelvin rating is so people can get that blue effect from their lights. That's why they have the kits that go up in kelvin rating. The different ratings on the kelvin equal what kind of color from your lights will shoot out. Like 4300 is White with a bit of yellow in it, 5000K is usually a diamond white, 6K is white with a bit of blue and so forth. The higher you go, the more blue the light gets, then turns purple and so forth.
I personally wouldn't get anything past 6000K if you want usable light output from a HID system. The higher you go, the more color you have in your headlights, which is bad when cops see it. Also having the blue style HID's do look nice, but its also harder on your eyes (Makes you sleepy) I have 5000K HID's on my Teg and I haven't had any complaints from anyone while I drive. If you are worried about glare or scattered light from a non-HID setup, you can usually point the beams downward so that it isn't as bad of a problem. A retrofit is the best way to go if you don't have any way of getting an OEM style HID setup. Seeing you are JDM front converted already, you shouldn't have that problem though.
You might be better off getting the Type R OEM HID headlights and selling your old JDM front headlights to someone that needs them for their conversion but doesn't care or can't afford the OEM HID headlights. Those will be way nicer and have a better cutoff than anything that's plug and play. I'm guessing you probably have the old SIR-G chrome housings? Or did they have black housing JDM headlights w/o HID (Older DC2's?)
Like I was saying though, stick to 4300-5000 if you do go plug and play. Usable light and no hints of blue what so ever and you should be okay with cops. Good luck on your choice.
