In house loans at a bank are not very competitive in most cases. Some banks have seperate divisions that may do auto financing for dealerships, and work directly with them, but the branches that you can walk in to do not have access to those loan products. Don't get too crazy shopping around, if different types of lenders put inquiries on your credit it will lower your score for a while. If they are all banks within a week or two, it should be fine. Find out where all the dealership sent your app out to. They may have broadcast it to several lenders already who have all checked on you. For the 1% difference, I'm guessing it's maybe $10/mo different, or $600 over the life of the loan? (based on around 20k, take if from there) I could be wrong. Maybe you can negotiate. The dealership makes money, a good bit, off of doing financing rather than you coming in with the check. Tell them to give you the $1500 and the rate, or come off another $1500 from the price, with the rate, and you come out on top. I think.
If you go outside for financing, get the offer in writing so they can't come up with a BS excuse for a higher price if you don't do your financing with them, to make up the money they lose by not doing the financing in-house. DO NOT let them quote you payments for your bank rate loan. Many have a "BS" sheet with inflated, false figures on it to spook you out of going to a bank for financing.
PS: I've seen a lot of people on here talk about
www.peoplefirst.com as a good online lender. That may be worth looking at.