Wait till the 15 come out. By then, used 5.0's will flood the market and be cheaper.
That way if you decide to get the 15... Awesome. But if you decide to go used, you'll save money.
2011 Black Mustang GT Premium
Corsa XO & Sport AB/Airaid/Bama 93R
Best 1/4 mile to date 60' 2.009
12.538 ET @112.33
100+ Deg 85 Hum RPR 3PM 1/2 tank street tires