Personally - I don't think you really stand a chance at gaining anything much more than silver. And with that you don't get much advantage - upgrades are too hard, and you will always find yourself chasing miles. In your case you might want to look into splitting your travel between JetBlue and AirTran/Southwest. To be honest their economy product is better than regular economy on Delta, and will probably cost you less, too. Plus no bag fees and you are in a JetBlue focus city, so many direct flights.