Just a heads up to some of you looking to purchase the DLC through Amazon.
I've been following this DLC list
HERE for details on which DLC I wanted to buy (mainly the costumes and equipments). So far I've determined that the Amazon games codes work for these packs:
New Costume Set (1)
New Costume Set (2)
This is Equipment Pack
It'll Come in Handy Pack
Hero (?) Pack
I don't know if it's just me, but when I bought the next equipment pack,
Latest Technology Pack, Amazon gave me an invalid code. Not just once, but
twice for this same pack. Of course I sent an email to the Amazon Customer Service asking for a valid code replacement or a refund for my orders, but because of this I'm going to hold off on buying more packs.

Not sure if there's a limit to how many codes you can input in a day...or something.
Well, at least the Costume packs still worked.