I would think twice about buying a car like that. They can be nightmares, so I'd recommend a car from a reliable brand. You can't ever guarantee a good car, but you will almost certainly be unlucky with an old Audi, Mercedes, or BMW.
I think you should be thinking more about reliability, so check out the 20012005 Lexus IS300, preferably one with lower miles. I found a 2001 IS 300 near me with 176,000 miles (not exactly low) going for $2,990. It has a sunroof, heated leather seats, auto AC, CD player and radio with 8 speakers, Keyless entry, cruise control, power driver and passenger seats, heated mirrors, HID headlamps, and fog lights. It has an inline 6 cylinder engine the produces 215 HP and 218 torque with a 5 speed auto. I've read that the ride can be overly stiff over rough pavement.
You might also want to look at the Infiniti G35, but probably won't be reliable.
A 2003 or 2004 Honda Accord V6 sedan or coupe will probably be the most practical for you. It won't have the same handling as the IS 300 or your Audi (although it's lighter), but it does have a 240 HP V6. This is the model after the one that had many transmission failures, so you'll probably be fine. I owned a 1997 Accord EX V6 Coupe and I really liked it but I needed 4 doors. I never had any problems with it.