That's how they're done - with seperate RGB controls. It's the "right way". The response of each individual screen is different, and the response of each channel can vary. When a monitor (LCD or CRT) gives you a choice of kelvin temperatures, it's just a "best guess" as to what will really be that temp. They're never actually that temperature, nor are they ever exactly white (or neutral).

With a hardware calibrator, you'll be able to adjust each color channel individually, and get white that is truly white. Then, it will generate color curves to keep the rest of the colors where they should be as well.

Note that just because white is white doesn't mean that grey will be grey, on cheap displays I've seen white be white, but grey be very purple or green. The response of each color channel is not necessarily linear, nor do all of the channels necessarily match each other in their response curves!