If you have paid off Amex and if the account is going to fall off from your report in few months dont even bother with any GW letters. Call CRAs and ask for early exclusion.
I had an Amex which I paid off this Sept and got Optima which was what they had offered you (not sure if you took it or not). After paying Amex within a month EQ didnt have Amex entry, EX and TU have also removed that entry. If they hadn't I was going to call TU as it was supposed to drop off in Jul 2016.