Amex has lowered their minimum scores without a doubt over the last year, probably in response to losing Costco but they are offering very low limits to those under 660 or so. Your scores are simply too low to get qualified with AMEX. I wouldn't apply for anything with anyone right now, my biggest regret during my rebuild was applying for cards that were a stretch and wasting HP's which held me back a bit. I would wait till you have Experian scores in the mid to upper 600's for AMEX. I would work on a rebuild and address the factors that are holding your scores down so when you do apply you get some nice limits and don't get denials.
Income won't outweigh weak scores, I know this from personal experience 200k of income low debt but crappy scores when I began my rebuild and struggled early on to get a 1k limit. Using the advice of the good folks here in the rebuilding section and within 6 months or so things totally turned around.
