I think that an Annual Pass is probably your best bet.
The Ultimate Park Hopper (Length of Stay) is $434.60
An Annual Pass is $391.14. This would get you into the 4 major theme parks, but you'd have to purchase admission to the water parks, Disney Quest, and Pleasure Island. I don't know if you're planning on doing those, but Water Parks and Disney Quest are $28.86 for each adult passholder. Pleasure Island is $17.15 per adult passholder. (That includes a $4 discount for annual passholders). I would say this would be your best bet. I THINK there might be a discount for DVC members, but I really am not sure. You'd want to speak to a DVC member, or call member services and find out if that is a perk you're entitled to.
If you go to Ticketmanis, you could get 2 5 day park hopper plus passes for $520 per adult. I would say that this is probably the LEAST desirable of your options.
Overall, I would reccomend the Annual Pass. Unless you're planning on visiting both the Water Parks, Disney Quest, and Pleasure Island, in which case I would reccomend the Ultimate Park Hopper. Something else to keep in mind is whether or not you'll be returning. If you are going back, then DEFINITELY get the annual pass.