Stock lights aren't wired that well. I would not overload the stock wiring with AUX lights. I'm not certain if they use relays. You'd probably be better off witing the lights independantly then having it on its own switch. If you wanted them tied to the headlights then you could have teh switch connected to the headlight switch +12v then they will be on when your headlightsare on but you can also turn them off as well.
I used the wires from the light switch as an ignition source for my aux lights; that way, if I can only turn on the fog lights if I turn on the parking lights (or the low or high beam, but at the very least, the parking lights) and I can only turn on my daylighters if the high beam is on. Of course, since I also have the independent switches, I can turn on only the stock lights. But it is kind of cool to have like this, because I just keep both the fog lights and driving light switches on, and when I turn on my lights, the fog lights come on, and if I turn my brights on, the Daylighters come on as well... I am happy with this setup. Oh, and yes, I only use the OEM switch to power the AUX switches; from there, they go to relays...