If you really do plan on going turbo, just stick with the GT engine. If you plan on going NA mods, I'd say with your situation you should go for the GTS swap. Right now there is way more out there for the GT, including the new TRD
supercharger that is supposed to be on the streets soon.
Or find a way to contact lotus and drop in their version of the Celica engine, if you really want to go all out