Rick S - another idea....
I have had experience with three car brokers and have been happy with the service provided by each. These brokers are people who either cruise the dealer lease-return auctions or consign autos for people too lazy to run an ad in the paper. The lease-return auctions generally focus on newer cars (just off lease return), but many dealers also bring in older trade-ins to see if they can unload them. All cars at these auctions have been inspected by dealer service people and the broker is given access to the write-up on needed or suggested repairs. I have had a couple of searches run by brokers for specific cars. You have to be quite specific about the model, year, options, condition, even the color, etc. The broker calls you from the auction if he/she thinks he has a good example in front of him. You've already discussed bidding (and his fee) and if his phone description sounds good, the broker will bid on the car. He will keep you on the phone during the bidding in case the bids get higher than your max - and will ask you if you want him to continue. If successful, he will bring the car to his lot, or office, or whatever, and permit you to take it to your mechanic for a pre-purchase inspection. You only buy the car if you're satisfied. If not, the broker sells it to someone else and continues to search for you. Some brokers ask that you sign an agency agreement with them which asks that you give the person the exclusive right to operate on your behalf (all sorts of legal implications) for a defined period (I did a month once). Others don't ask. There are good, honest brokers (I found two here where I live) and they can find stunning cars. The price that you will pay is the wholesale bid price plus the agent's fee, which can be much lower than at a used car lot or even from a private party who knows the value of their car.
Had I not had a career turn awhile ago, I might have closed the transaction I had going for that 2-year old BMW M3....(sigh).... My wife is happier I have the 300E.
As to a Benzmac Certified program, sign me up. I want a 500E at some point.
2003 Dodge Durango SLT
2002 BMW E39 530i Sport
1988 Mercedes 300TE
2003 Chevrolet Suburban