The bumper on the 03-04 is identical to the SE bumper. The SE just has those little grilles in the cutouts.
03/04:
http://cdn1.3dtuning.com/info/Porsche%20Boxster%20S%202003%20Coupe/factory/4.jpg
SE:
http://www.mad4wheels.com/webpics/hires/00000465%20-%202004%20Porsche%20Boxster%20S%20-%2050%20years%20of%20the%20550%20Spyder%20Annivers ary%20Edition/2004_Porsche_Boxster_S_-_50_years_of_the_550_Spyder_Anniversary_Edition_00 4_6203.jpg
I just think it looks sort of unfinished without the grilles but wanted to know what kind of work is involved in affixing them. I think would be a great little mod if it turns out it's a 5 min job.