I agree with both David and Larry.... If you are going to HID, you may as well get OEM ones... aftermarket retrofit kits can be had for 450 - 600 bucks if you shop around... but they may produce more unwanted glares than OEM ones....
Also, HID significantly improve night time illumination of the road, and especially the road signs.... but it would all depends on what you really looking for... for HID Look, you can save some $$ by going with brand name bulbs(PIAA, Porlarg).
1992 Mercedes-Benz 400SE
2002 Acura TL Type S