I went also have XXR's and had to make the same decision on front rim width. I went with 7", as I thought it a better width for my 215/40-17 front street tire size. I'm a roller, but haven't driven yet. Most tire manufacturers spec 7.5" nominal for a 215, but either is within range. In general, stretching the tire on a wider rim can increase feel and turn in response, whereas pinching it on a slightly narrower rim can generate a bit more ultimate grip