I understand that many people are hesitant to try Priceline bidding because you don't know in advance what company you will get and because once the deal is done it's done, with no changes or cancellations, but we've had great luck with Priceline.
I just got a mini van at MCO for January 15 thru 23 (8 days) for a total of $347 through Alamo by bidding $30 a day. That's only $304 a week TOTAL!
We've taken January trips several times so I know this is about as good a deal as anyone will get.
Our recommendation: bid really, really low, expecting it to be rejected, to get the feel for the process. Then two days later you can bid again and try to get it at the price you want. You will see they show you the total price before your bid is accepted, so no bad surprises there. Compared to the Alamo site I'm saving over 60%.
Good luck!