I have an Amex SPG, Amex Premier Gold, Amex Blue.

Amex Blue is just because I wanted a credit (not charge) card for a tradeline ... I have a 20k limit which I rarely utilize more than $1,000 a month on... so it just looks good on my credit report.

Amex Premier Gold is what I use for all airfare and to rack up MR points with "regular daily" charges (everything except Gas which I have a different CC for). If you are planning to put more than 30k a year spend on the Gold card, its a good bet. Less than 30k/year and its probably not worth the annual fee.

The SPG card I really only got for the signup bonuses, once annual fee is due next year, will probably cancel it. But if you are not going to be spending 30k spend on a Gold card annually, this is probably the best Amex around (though you have the Hilton, so not sure you want 2 hotel cards).

Dont bother with the "regular" gold card. Cant speak for th Green card.