SoRCon 8 27 Feb - 1 Mar 2015 Basildon UK http://www.sorcon.co.uk Essex Games 27 Jul '15
That's right. No duplicate power cards can be played in the same phase, including scoring cards. So if you get a duplicate scoring card in the New Kingdom, it is one gold.
You can of course choose when to turn it into gold. If it's a card that someone else can score with, hold it until either you need the one gold or the deck won't be shuffled again.
(In some circumstances holding tje card could also have a bluff effect. But that's uncommon.)