Given that a stock celica of that vintage would be worth $7-10K I'd suggest that yours would be worth around $10-11k.
Just like yourself - a lot of younger people buying coupes want a turbo. The import of all these 180's etc has had an impact on the re-sale of locally delivered coupes. Comparatively, they are slower and more expensive than the grey imports. At least the local cars are (in general) more honest and of a higher quality...