Since you asked for an opinion, I'll say that your car looks like an EX with Si wheels now. That's either good or bad depending upon your preference, but I applaud you regardless for testing it out.
I do think that you'll need better plugs, specifically ones that have some sort of "seal" to prevent moisture from seeping into the trunk. Another option would be to do a trunk swap with another LX/EX owner. I can imagine there would be one or more individuals with your same paint color that might love to own a Si spoiler.
Just food for thought.
On a different note, this Rogue Double Chocolate Stout I'm sipping on is phenomenal.