I prefer to buy through CDJ early after the CDs are released and pay through PayPal funded by my bank card.
If the weight/shipping prices go up due to bonuses of the item being heavier than first announced, paying by PayPal means you don't get charged extra shipping
When I ordered the DejiDeji I got upgraded to better shipping because the book exceeded the size for the cheapest shipping!
CDJ will definately add the poster+shipping for free if you've paid by PayPal through a bank card (not VISA etc)