Search, guys, c'mon!
Remember ROY G. BIV? Yup, headlights work the same way:
First of all, the K rating isn't wattage. It's Kelvin, a reference to temperature, specifically, the color temperature at which the gas inside the bulb is burning; why we see the color of the bulb as it is.
Anywhere from 5-6000Kelvin
is where you'll get that white color you're looking for. Higher than that, and you're headed toward blue, and eventually, purple. Due to variances in manufacturing, hardware, and other factors, some lines of HID bulbs burn at different color temperatures than what's printed on the box. Some brands of HID bulbs, you'll buy a 5000k bulb and it'll still look amber; others, that same 5000k bulb might look bright white with a tinge of blue. Just like any other mod with so many options, YMMV.
I personally recommend the Kensun kit on Amazon. Prime eligible, decent price, many, many good reviews, and hella customer service. I ordered about a week ago, received my kit, and although I haven't installed it, yet, Kensun has already emailed me asking if I had installed it yet and if I had any questions. Did I mention that they've got a two-year warranty?
For more information on HIDs, search.