The Pro Duo cannot do 1kh/s, it's practically 2x R9 nano, one nano does 250, if I remember correctly or around that mark.
There's no difference between a nano and a fury x except for the cooling solution and the nano is less power hungry...
The clock speed is lower but if you cool the nano properly, it's the same.
http://i.imgur.com/B9bNTzd.png