I just recently fitted my 2004 Nissan Altima 3.5SE with a set of HID lights. It just so happens that I went with the Philips Ultinon 6000K Conversion Kit. This is the best kit in the world used by BMW and Lexus. It is NOT street legal but I take the risk anyway. If you want the stock and legal route for your Altima go with the Philips 4100K which is OEM on Nissan Altimas. The Kit I used cost me $596 while the OEM style kit cost $548. These are the best prices around at
www.brightheadlights.com The investment is well worth it over the stock halogens. I forgot only go with the brand names Philips and OSRAM if you decide to buy not imitations out there like McCoullah,Bohman-short life hurt vehicle