We are also looking for fares from Buffalo to Orlando. In my experience, it's substantially more expensive to fly out of Toronto even before adding on all those extra fees Pearson Airport charges. We still have quite awhile before our trip, so the flights are still pretty expensive, but I have noticed they have come down a bit since I started watching them. I've had really good luck with expedia.ca - that's where we booked last year for $210 pp Canadian tax incl. I've also been using sidestep.com - it's a program that will compare airlines and prices to other sites for you.
Keep in mind that orbitz.com sometimes has better deals, but will not allow you to book with a Canadian credit card.
Just a few ideas... good luck.