Holiday times can be a nightmare. I have booked for Easter next year from Atlanta airport, 16 nights, Alamo quoted over £900 (has dropped a little since to over £600) about 3 times what I expected. Paid £376 in the end, still more than I expected but far better than Alamo.
Let me know dates, size of car and best price you have. I will have a look and see if I can see any better.