I just sent a friend an Amex referral link and it had a 75000 bonus for a new Gold card, so if you don't want the double like brc01 suggested, I'd sign up for a new one instead.
And keep in mind when upgrading that you need to keep the NEW card > 12 months even if your renewal hits sooner (since the renewal would be based on your Green date). You may not be able to keep the points and downgrade or close it without paying a second AF with an upgrade. li