Do you mind If I may ask how many inquires you have on all bureaus. The reason I ask is because I think you could try potentially for another Amex in 6 months or so, because a 628 is not good...lol. If you have a lot, that could explain your score, and your chances of getting approved for additional cards.
You really need to hold off on more apps and garden. 628 is pretty horrible, and definitely not a score with which I would use to apply for additional cards.
CreditScholar- Was that post meant for me or for the OP? AFAIK, my scores are 700+...but I'm not sure who you were referring to in your post. I agree, OP, your scores need to be at least 680+ if you want a shot at getting good cards with good limits..IMO.