Are you planning on going to the parks all 8 days, or are one or two days "travel days"? If so the AP might not be "break even" for you.
What you CAN do is purchase PHP's before the rates go up in January. If Disney decides to go back to room only AP rates after the first of the year, you can convert any pass into a more expensive pass (i.e. PHP into AP).
THat way if the AP room rates DON'T come out for March, you'll have your PHP at 2003 prices.
If there ARE AP room only rates for March you know you can upgrade your PHP's to AP's. You don't need them at checkin. You can explain at checkin that you will have the AP's later that day or the next day.
If you convert to AP's at the 2004 price in March when you arrive it will be because it works out best for you financially. You won't be freaking out about waiting for AP room only rates. It puts you a little more in the driver's seat. Although you won't techically get the 2003 AP price, it may decrease your stress level in waiting for those pesky room rates.
I would also advise NOT using the MK guest relations window, it's always mobbed! Epcot is historically the least busy guest relations window, where you exchange your voucher for real AP's or upgrade the pass you have to a longer one.
I hope I haven't confused you!
Enjoy!