HID projectors, into stock housings, with enough money I'm sure you could, but it would seem pointless, where the stock housing is not 100% clear, where an elipsoid would benefit.
If you want projectors, your best bet is to order a set from online stores such as autodynamic.com, they should run you no more than $170 or so. However, I still don't suggest you put HID's in these 'cheap' projectors. The projectors that are on BMW's, Audi's, and even Integra's are made differently.