Why is it that BMW's site shows a 5 spoke (which each of the 5 being split into two) 16" wheel for the SPP on the 323i, but then I do a search on autotrader.com, and pull up 100s of 323s having the 7 spoke wheels of the 328i SP? Are you charged extra if you want the 7 spoke wheels, and will they be 16", or will they put 17" wheels on a 323i?