Answered By Curtis Arnold:
American Express is a CardRatings.com advertiser.
That is becoming a common question as more people become credit savy. It sounds like you have the potential at that spending level to earn some nice cash rebates. My only concern is that you may occasionally carry a balance. Carrying a balance on any rewards credit card is a bad idea and can easily wipe out any rebates that you might earn. In fact, you could easily end up in the negative.
So, in general, I would suggest that you use a low interest credit card for purchases you know you aren't going to pay in full and a cash back card for all other purchases.
Some of my favorites are the Fidelity cards which offer up to a 2% cash back rebate. I also like the TrueEarnings® Card from Costco and American Express.