yup, just went through this over the last few weeks as the wife's 10 year old and well paid off Benz was totaled in a low speed fender bender
I'll share what I've learned
Carvana is a really cool service that shows a lot of great info and has a strong selection of cars at great prices. When you dig beneath the covers you will find that 99% (of the ones I checked anyway) come out of New York, NJ, PA and CT. Seems the Auction prices are lowest in the NE, especially for 4 wheel drives so they buy them there, truck them here and mark them up for a nice profit. I didn't want to buy an off lease car that spent 2 years in Manhattan personally, you may differ. I keep my cars for forever so I'd rather have something that began it's life better. For that reason I wrote off Carvana even though the nerd in me really wanted to work with them.
Atlanta Luxury Motors, ALM, you will see all over cars.com and autotrader does the exact same thing. Follow the carfax closely a few of their cars are local but most are Northeast as well.
I ended up buying a Lexus at one of the local dealers on one of the last days of the year. From my perspective CPO is the way to go if you find a good CPO program like Lexus. Costs a few bucks more but for Lexus seems worth it. Comes with 2 year unlimited mileage warranty and the first 4 service visits which for me includes the 60K mile service. Some of the CPO Programs seemed like they were marketing only and didn't really offer much. Buick comes to mind as we were looking at the Enclave.
CarMax, to me, seems high priced and many of their cars came from the same Northeastern Auto Auctions. Seems there is a good bit of profit to be had buying low there and selling high here.
I'll also mention that Atlanta is really, really high priced. Expand your circle to Chattanooga, Charlotte and Birmingham and you will see decent price reductions. Get into South Florida and the prices really really drop significantly. I had a CPO Lexus in Palm Beach that I was trying to buy over email and have shipped back up. Dealer and I were back an forth on a price and someone local scooped it up while I was playing the "I'll wait on you to accept" game. Fortunately a near identical one showed up in Atlanta same day. I went to the dealer and made him an "I'll do this today for X" deal on 12/28 and he bit. I'm very happy with the new ride though I was hoping to go without a car payment for another year or two that I thought I had left in the benz. Oh well
good luck with it