HID Xenon Conversion Kit ?????????

I have a 2006 Volvo S40 that has the none HID xenon projector headlamps. I need them to be brighter because well they suck. I been looking in to doing the HID kits but wanted to know if it would work with my car because of the projection. Could I use the ballast I have in the car or do I have to you use the ones in the kit? I guess I want to know the best way to do this and still have the projection work. Thanks!