You have owned quite a few impressive cars. My dad had an '82 BMW 728i, I loved the shark-nose look of that car.
My '02 WRX and 370Z are the only new purchases I made, the Subaru being my first new purchase. I had originally planned on upgrading the WRX a year or so ago. Because of that, I had some extra cash saved up, and was able to purchase the 370Z before selling the WRX, and privately sold it. I agree, trade-ins add an unrequired complexity to the new car buying experience and the dealer ends up with the upper hand.
As far as the 370Z goes, one of the main reasons I purchased it was because it has a lot of technology, especially compaired to the Mustang and STi that I cross-shopped.