Ashley, never, never ever place a stop order with FXCM. Trust me. Just dont do it! But maybe you should figure out for yourself ;-)
Quote from Jason Rogers:
Hi Ashley,
A stop loss order would act the same way since both orders (stop loss and margin call) will execute as At Best market orders. While the margin call gets triggered when account equity falls below the margin requirement, the price at which equity = margin requirement may not be available. In this case, the trades will close at the price at which liquidity is available. The execution risks page on the micro site also has details in the section titled "Margin Calls" http://www.forexmicrolot.com/trading-execution-risks.jsp.
I hope that helps.
Jason