The selection of 15" tires seems to be shrinking fast, other than specialty shops like Coker, Mickey Thompson, Hoosier and big meats for Jeeps and off roading; and the selection of 16's isn't a lot better! One thing to think about is how you would deal with a tire problem on the road. Having to buy two wheels & tires to get home would suck, but the alternative might be sitting in a hotel room for a few days waiting for an order from Speedway, Summit, Coker or Amazon.
I think I'd be looking at 16's minimum, and maybe 17's. Just my $0.02.