Thanks for all the info! I think I'm going to go with the Pearl Izumi Vagabonds, they were the most comfortable that I tried (and conveniently the least expensive). I went to the podiatrist a few weeks ago, and he didnt say specifically whether carbon was preferable over nylon or not, but rather that I just need cycling specific shoes that have (relatively) firm soles. I am also getting custom orthotics from him, but he said they wont fit in cycling shoes. I will look into the other insole options for sure, and I'll see how my feet feel once I start riding with the right shoes.