I personally think the deck lid that comes with the DX/LX/EX looks better than the Si spoiler. It just looks a little classier in my mind than the tacky Si spoiler. I am a cardomain regular and have seen people install the Si spoiler on their LX/EX without removing the stock deck lid. It looks unique, little too ricey for me. I will post you a link to a picture with both spoilers if I can find it.
The ones I told you about (the ones I thought I saw on cardomain) are unfortunately not an Si spoiler. This is a picture of a white LX with the stock deck lid and a taller (more like a Lancer Evo) spoiler.