BEH

I did the same thing and am pleased.
I had my trade in, a 06 BMW 330i, appraised by the local BMW dealer for trade in value then went to the local Audi dealer.
After talking to the salseman for about an hour he introduced me to the Sales Manager.
This is where things went down hill.
I told him I don't have time or the inclination to hassel and asked him to give me a firm price including trade in and told him I had the BMW appraised at the BMW dealer.
He told me that is not the way things are done and to go to BMW and get them to buy it.
I then went to another dealer closer to work and asked them the same thing.
Within the hour I got an offer in writing via E Mail including what I wanted for the trade in.
I might have gotten a slightly better price if I haggled back & forth but I hate that.
This way I got the vehicle I wanted, didn't have to go through the agraviation of selling my car privately and all in all a pleasant experience.