You just have to play around with different dates and see what comes up as cheaper. I check out disneycruise.com and do their rate quote. I check a bunch of different dates since the rate can vary from cruise to cruise.
The one thing to consider is that Disney rooms are pretty big compared to other lines. I had to get a cat 1 on Celebrity (Millennium class ship) to be about the same size as my Disney cat 9. The bigger rooms are part of the reason it costs more.
Personally, if you can swing the RC cruise, I'd go for it. Keep checking Disney and do that when you can. Booking years in advance can get you a pretty good discount. Maybe you can look towards 2004 when those rates come out. You'll get a great early booking discount then. Also, cruising during hurricane season is much cheaper. We've cruised twice in hurricane season and had beautiful weather, but are always prepared for rough seas and port changes.
I also recommend booking with
Dreams Unlimited. They always check for lower rates for you and are so helpful.