I don't think the DSE tubs most folks use will allow a 13" wheel but not sure and a 12" wheel will weigh less and handle the same tire. While you're considering larger staggered diameters, remember most wheel & tire companies make 19s so you can run the same rubber as a 911 Turbo, Viper or Z06.
And lastly, 3 piece wheels are a little spendier but they look bitchin'! If you don't have H.R.E. $, try
www.dpengineering.cc or
www.forgedwheels.com and when in doubt, hire a designer! Ben has also chimed in with intelligent input on this thread too along with other very talented guys that frequent this forum so pick a favorite and somebody here can help you make that all important decision.