Mike Focke has a link to the option decoder that is invaluable for your search.
I believe the options info page is glued inside the front trunk lid, correct me if I"m wrong. Several used places will have a photo of this sheet in the car hotos so you can verify the factory options. Instyle Auto in Pompano Beach, FL does this. They have 60 Boxsters!!
The option decoder link is
http://www.kindel.com/Porsche/options.asp
I'm also on the search for 03/04 S - Seal Gray with Graphite Gray interior, 18's, Bose, Litronic.
Kurt