First off, sorry to hear about the accident and hope everyone was okay.
I used to work for a company that serves auto dealers from the back side, so I have a little experience with them. You will not get your best deal at a first tier dealership IMO. In fact you will get ripped off more times than you know. The price point you are at (if buying from a first tier dealer) is not going to produce a car that will replace your van, and be in reasonable condition IMO.
First tier Dealers (Chevy, Ford, etc.) do not like cash sales, as they make money on financing as mentioned earlier. Plus a dealer is selling you the car at a 40% markup from what they paid for the trade in, and the used car salesman is commissioned on that so they usually don't like to deal on the price like they do on a new car. The reason some will deal on a new car, is because of manufacturer and finance company kickbacks they get that you don't even know about.
Second tier dealers (non manufacturer dealers, small side of the road lots), get most of their cars from auto auctions where the sell repo's, first tier dealer vehicles that did not sell quickly, etc. They love cash sales as it free's up their cash flow quickly, and financing is usually more of a hassle for them than it is worth. They are usually not a whole lot worse than buying from an individual as long as YOU DO YOUR HOMEWORK FIRST. If there was something wrong with the car when they got it, they may not have done the best job of fixing it, so if you find a car from them, you will want to have a independent mechanic that you trust check it out for $50 or so..
Find a good car from a private owner or second tier dealer, spend $25 for a Carfax, $50 for a mechanic inspection, and check out carsurvey.org for user reviews of thousands of vehicles to see if there is anything you need to look for. MSN autos is great for user reviews as well. Do the research before you go to look at it. Also check the private owner pricing on Kelly Blue Book (kbb.com) and Edmunds.com. That will give you a good idea on whether the asking price is reasonable for the car.
You will get more car for your buck by doing a little homework, and using classifieds, craigslist, etc. Plus dealing with an individual is far less hassle. If buying from an individual, just make sure you pick the car up during BMV business hours, so you and the seller can go get the title change filed right away.
Most of all TAKE YOUR TIME. This is a decision you will have to live with for awhile. Anyone who is pushing you to make a fast decision, be it dealer or individual is looking to rip you off somehow. You can find a good deal for your $6k budget, but you need to do the legwork to make sure you don't get someone else's problems. Either a first tier or second tier dealer are trying to make money off of you, so they are not your friend. And many private owners are trying to get rid of a problem, so they may not be your friend either. Make sure in any case you budget for the Carfax, mechanic visit, and most of all do not buy a car the first day you see it. Go home, talk it over, spend some time online to see what experiences other have had, then go back and drive it again. Crawl underneath and see if there are any goofy fluid leaks. You'll do okay, but you are the customer, so you are in control.
Not to hijack, but I actually had a dealer get mad at me for taking about an hour crawling under, over, etc this car we were looking at. He kept trying to push me for a decision, and everytime he did so, I promised myself silently that I would spend 10 more minutes checking the car for problems, just to irrate him. Eventually, I found why he was pushing me. The axle boot on the front end was leaking grease, and after I called him on it, he refused to fix it. I left as quick as I could.
Not that I am trying to guide your decision, but when I was in the market for a minivan in about the same price range, the best one I came up with was the Mazda MPV. They seem to last for a very long time with minimal maintenance, and we drove one and even DW liked it (and she hates minivans). There are a couple in the Atlanta area on Craigslist well within your budget.
http://atlanta.craigslist.org/atl/cto/1648747141.html
http://atlanta.craigslist.org/eat/ctd/1651541475.html
http://atlanta.craigslist.org/eat/ctd/1649783790.html
Good luck with your purchase, and report back to let us know how it turns out!