k bro, heres how it goes. to answer ur question short, yes, you can put a HID kit on ur headlight and the projector will function. you might want to reaim the beam of the projection if you install the HIDs. BUT jsut by getting an HID kit, dont expect the streets to illuminate just like the s2000 or BMW headlights/HID light up the streets. the reason why the s2000 projection/light output is so nice is because of the projector. all OEM HID kits (that means HIDs that come stock on cars, any cars) come with 4300K light output. the reason why a lot of ppl buy over 4300K HID kit is because they want a blueish color. once you go over 4300K, you lose brightness/light output and gain color. the reason why BMW 7, M3, honda s2000 have that blueish color in the light output is not because of the bulb, its because of the projector. the s2000 projects a prismic light that shakes with every bump the car goes on is cz of the projectors.
so expect some light output from ur stock projector. if you put HID kit on ur stock headlight projectors, ur light output is not gonna be as nice as audis, bmw, and all these others that you want ur lights to look like. unlike HID projectors, celicas projectors arent made for HIDs so the light output is messy comparing to a s2000's. ull notice that there would be extra glare created from ur lights because the HID is not being beamed correctly. you wont have the cutoff lines like an s2000s. you noticed the OEM HID kits usually put a light from a certain line to another facing it, meaning you can really see where the light ends and cuts off and everytime the car bumps the cutoff moves and you see its a line where no light is being projected after that. ur not gonna get that from stock projectors.
to make things short, ask urself wut you want. do you just want color and dont care about output and the way it looks and have others blinded? 6000K HID bulbs will create blue color but the output is gonna be WEAKER than the stock bulbs you got.
if i were u, i would save some money and do it the right way or else not do it at all. get 4300K HID kit, best brands are hella and philips, and get valeo projectors. valeo projectors are the same ones used in a lot of euro cars (audi for example). in order to install the projector though you need to open the headlight assembly and put the new projectors in.
i typed enough for the day, for more info goto hidplanet.com, search on this site cz there are a few informative posts, PM me or erick for other questions if you need.