Recently, I purchased a 2011 328i convertible. The trade in offers of approximately $5,000 on my 1995 325i didn't seem to reflect the vehicle's value. The vehicle has one owner, only 48,600 miles, is clean, and has mostly original parts. I'm not exactly sure of the definition of classic or vintage models, however, this is one good looking red convertible and it performs extraordinarily well. It would be appreciated if you could provide any direction in selling the vehicle.
You certainly won't get the most for your used car as a trade-in. You would definitely have to try to sell it yourself to get the most out of it. There is certainly a market for this car but you will have the inconvenience of marketing it and it may take time/effort/money on your part. You have to first decide if the "hassle" is worth the difference. You should look at the Roundel marketplace to see what other similar cars are going for. Also, look at sites like Autotrader.com and KBB.com to get an idea of what it may be worth and e-bay motors completed listings to see what similar cars actually sold for. I have sold 2 cars on Autotrader both within 1 week of placing the ad for close to may asking price. Also, put the car in the Roundel Classifieds too.
Sold my parents' '94 325iA sedan w/115K (I think) miles for just under $5K about a year ago. A quick ad in the Roundel and it was gone within 2 weeks. Car was in pretty good shape, all records and maintenance up to date + it had new tires. I tried autotrader.com first but that was a waste of time.