The Sapphire card earns CO miles and recently had a promotion for 25,000 miles with no fee for the first year.
The best CO card (which gets you 1 free 50 pound bag) offers that I've seen is 25K with the fee waived for a year or 30K with the fee.
Of course the best card to hold is the Presidential Plus card, which gets you all elite benefits, 2 70 pound bags, and PClub access.