Definitely price it all out, and check out the various codes and coupons you can find on mousesavers.com. I've never found an off site rate that's better than at MCO, but I know there are more variables than you can imagine!
There are also often threads on this forum for different months, so be sure to seek those out, to try to get the best deal. And don't give up checking, even after you've booked, if you've booked a rate that can be modified or canceled. We've rented from MCO three times now, and each time I've been changing the discounts around on it to get the rock-bottomest deal I can get, in the last couple weeks before the trip.