Can I just replace the stock Halogen bulbs with Xenon lamps?
No. Standard 12V automotive power sources are incompatible with the HID light source. The standard halogen bulbs run at 12V, while HID lamps run at approximately 25000V and require several amps to start up. The additional hardware that comes with the kit is needed to convert your car’s 12V power source to drive the HID system. The connector is also totally different from any automotive halogen bulb connector.