Citibank will not even let you use a Citibank AMEX to fund a Citibank account. So, 'real AMEX' vs 'Affiliate-AMEX' makes no difference as far as I know.

If you've searched through FT (as I have), you'll notice that there is no information about using an AMEX to fund a bank account, thus, you'll have to figure this one out on your own (if such an option exists for any bank). I highly doubt just posting a question in it's own thread (that has already been asked in the myriad other threads about account funding) is not going to garner any additional information unless a newbie has come to flyertalk with information that the veterans here don't already know (unlikely). Nor will pm'ing a guy who has already posted all he knows about account funding with CC's.

That said, your best (and only) shot that I know of at this time is an IRA contribution to BofA that you can do each year (under their current rules anyway). They said they run everything except Discover as a purchase. I personally only used Mastercard for this, which did work, thus I can not guarantee your success with AMEX even there.