Hi all,
I'm currently in possession (11months) of Citi AAdvantage Platinum World Elite credit card. Few months ago became actively interested in earning miles as I found this forum and other blogs.
The card itself is okay - I have $6500 credit line (no late payments, though the score is in range 660-680, dropped due to short credit history) and I was able to get signup bonus of 50000 miles, spent them on roundtrip LAX-DC and one-way to Atlanta after few months.
Now I discovered a whole new way to earn more points - shopping portal, dining, hotels&car rentals, concerts, etc. This makes me stoked and I feel I can easily take advantage of all of these on a daily basis.
However, I'm looking at the other rewards programs and I have thoughts, that I might be earning more with them and at the same time earn AAdvantage miles (as it's not tied to any credit card, in fact). So the idea is to close AAdvantage citi card and:

1/ Get ThankYou Preferred Citi credit card - 3x on travel&gas and 2x on dining everywhere.
2/ Get Chase ultimate Saphire Preferred -2x travel, 2x dining worldwide (I travel at least 2-3 times a year)
3/ Get American Express Premier Rewards Gold card - 3x travel, 2x dining (US only though)

The main idea - is that I can still use any of the above cards with AAdvantage program, right? (as it is card-agnostic) And, I guess, they won't close my AAdvantage account if I close my card. So when I use my new card through a shopping portal (or add it to the dining) I'll earn miles in AAdvantage and points in other rewards program, won't I?

Let me know your thoughts!

More contextual info - I spend around $1.8-2/monthly, eat out $200-300/monthly, everything that's possible - I load on credit card, pay out balance in full every month.