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Is your primary goal to maximize the growth on your Amex? Or is the fact that many of your cards have matching credit limits the impressive part?
I don't personally have experience with Amex, but I always hear that "High limits beget high limits." Unless your credit lines are already near your income, I suspect a faster way to grow your Amex is to show them that you can handle cards that have higher limits than theirs.. and give them some friendly competition to match or exceed on their next cli.
i sort of want to appeal to a more conservative brand of lenders. i figure that might appeal to them with this approach (amex), since my income is lower than most.