Cheapest option is to buy the game from Amazon
, then use the codes to update your account.
Since Seekers will be released soon, buying the Seekers Collection
and using the 25% code is also an option, but be aware you cannot access the content/codes until its actual release date.
The codes are independent of their platforms, but locked by region. Edited, Feb 22nd 2013 1:04pm by xypin