The a la carte add-ons American offers are never worth it IMO. There are nine boarding groups and buying the priority boarding doesn't put you in group one, it puts you in (iirc) group four, which means while you will definitely find a place for overhead luggage, you also still need to stand around while everyone starts crowding the main boarding lane as groups 1-3 are called to board and play the "excuse me, are you group X? excuse me, are you group X?" sorting game. The upgrades to first class, main cabin extra, and preferred seating never really become better priced either, even if the flight is empty. Especially do not do the "$80 for 800 more AAdvantage miles" options they give you, which (again, iirc) over-value the miles by 5-10x.
If you fly American a lot, the branded credit card is the way to go. Not sure if the same is true for the other carriers, but I'd suspect it is. Even with the most basic economy ticket you get most of these optional add-ons (one checked bag, better boarding position, select your seats) as a cardholder. Credit card spend also counts towards status qualification for AA now, so CC spend can get you across the line to gold status if you might not have made it otherwise, and at that point you'll start to get upgrades to business/first on flights where everybody on the plane doesn't also have status. That will put you in boarding group 1, which, hey, mission accomplished and you didn't even need to spend $29 at the kiosk :).
If you fly American a lot, the branded credit card is the way to go. Not sure if the same is true for the other carriers, but I'd suspect it is. Even with the most basic economy ticket you get most of these optional add-ons (one checked bag, better boarding position, select your seats) as a cardholder. Credit card spend also counts towards status qualification for AA now, so CC spend can get you across the line to gold status if you might not have made it otherwise, and at that point you'll start to get upgrades to business/first on flights where everybody on the plane doesn't also have status. That will put you in boarding group 1, which, hey, mission accomplished and you didn't even need to spend $29 at the kiosk :).