If you really want an 09, shop around for the best price, first.
You now have the info to set up financing. See what your bank will charge you for interest with that dollar figure in mind. You now know how your credit is and what the interest rate should be. They will calculate your monthy payment.
You don't buy a car on the monthly payment, only. You need to know the price of the vehicle and the interest rate being charged.
How did they reduce your payment by $100? Did they lower the price of the vehicle? Did they come up with an interest rate that really is not available to you? Did they take off the back end purchases like a service warranty, mop and glo, high end ad-ons? All of which you will try to be sold later.
To make a large purchase, you want to be armed with as much information prior to signing anything. Spot deliveries are getting to be the norm. They get you sign and drive only to call you back with bad news on financing and then change the contract. Don't let this happen to you!