GDAX, Gemini, and Kraken all require identification. I'm trying to go through Gemini and Kraken, though, because they have passport as an option instead of a State ID (which I don't have). With Poloniex, I don't think you can go from fiat-to-crypto and their customer service is probably the worse out of all four; in my case, I currently have $200 in SC locked up and am waiting for them to rebroadcast the transaction.