When I applied for a Cap 1 no hassle Auto loan in 2006, my scores were between high 500's to low 600's. I had a repo in 2005, several late payments on credit cards and a Nextel collection, I thought I had no chance but I was approved for about $19k with 14% APR.
The APR is high but I had no other choice. The little old Mitsubishi I drove had all sorts of problems and was not road worthy.
I drove my old car until one day, I got a flat followed by another flat in the same week. Fed up with the problems, I decided to use the blank check from Cap One, 2 months after I received it.
Today, I'm still paying the loan. Capital One is not my favorite, they have low ratings in my books, but I am grateful that they offered me the loan which eventually helped my scores go up.
I would like to re-fi but considering trading it in for a hybrid. I may have to pay more since the amount I owe is more than the depreciated value of the car but since my credit has improved, I can probably get 5% or more reduction from the current APR. I plan to finance through the dealer this time if I decide to change my car.
Give Cap 1 a try. I don't think your scores will take another hit since you're car shopping. You have 30 days from your first auto loan inquiry to apply for other loans but I've read 15 days on this board also, so you may want to search the threads.