Honestly dude, coming from a Nissan Z car guy who is required by Nissan law to hate Supras, you should keep this car. Don't trade it for those cars you listed that you see everyday. Their value is only going to keep going down until it plateaus eventually, and slooooowly starts to rise years from now. You have a car that will only appreciate in value and is a clean example, even though it's the non turbo verison.
If you're bored with it, or don't have the money to hotrod it, just park it and drive some cheap car on a daily basis and you will have a renewed interest in the car in no time. I have a clean 92 twin turbo 300ZX I've been entertaining selling and no one wants to pay for clean examples of Japanese supercars. They just want to trade stuff you see all day long...there's a reason they want to get rid of their car and get something you don't see everyday.