one from a newer gen should still fit. I have an 05, and someone else that competes has an 07. The bigger problem you're going to have is aesthetically getting a gps antenna for your car. Mine has the factory sharkfin on the back, and I'm not sure how that's wired in.
And yes, it does look like I have two radios, but this is a good thing to me b/c I can take the faceplate off the bottom one and it's not anywhere near as noticeable, i.e. people won't bother your car as much.