I use
www.bitfinex.com because I really like their trading platform and website layout/design. You can do Limit, Market, Stop, Stop-Limit, Trailing Stop, and Fill or Kill trades.
They have most of the main alt coins so I trade there and transfer my BTC/LTC/ETH to Coinbase when I want to cash out (I live in the US).
Bitfinex is based in Hong Kong (I believe) and doesn't do transfers to US banks any more (because the US rules and regulations mean it costs far too much) so just use Coinbase to withdraw like I do.
Bitfinex have banned all American users.
OP - have a look at the following list, which shows all the exchanges that trade Ether:
https://coinmarketcap.com/currencies/ethereum/#marketsThere are American exchanges on there like Gemini (which is owned by the Winklevoss twins and is licenced and regulated).