Try looking at the transportation forum. They have deals listed for the month you plan to go sometimes.
I think Budget is the lowest for one way rentals. You can always use a comparative car rental website like rentalcars to see if you are getting the best deal.
Also, think about where you shop, bank, and pay with for discounts. BJ's,
Walmart, Visa, Mastercard. Nine days should garner a nice discount code. Think small instead of big. My local grocery store, Shaw's-before they were bought out, twice over-used to have a rental car code that was hardly ever used. Codes can be maxed out on uses so Visa and Mastercard usually aren't so grand. USAA, if you have it, is also a great rental car code.
If this rental is for 2018, a lot of codes don't come out until the new year. robinb is right. It doesn't hurt to book this deal as long as you are not putting down a credit card or booking it under your membership, or advance booking. Check the cancellation policy of your booking. Most of the time it's nothing to cancel, but sometimes you are looking at having to cancel it at least 3 days before hand in order not to incur a penalty.