Have you thought about JetBlue? You can transfer Amex MR directly to JetBlue instantly. They have multiple direct flights from JFK to STI all day.
Just ran a sample search Aug 7-14 and got:
Airfare (in points)
30,900

Taxes & Fees
$97.10


Granted, that flight in cash would probably only be $340-$450. If you don't have $800 to book 2 tickets, then burning the miles is your best use in my opinion. If you have the cash, then it's a really low redemption value, but they're your miles so use them your way.