I assume you are only looking at the manual trannys! If you are geting an auto, forget anything about preformance and just go for the styling of the car.
You are doing right by asking about modding question now. I use my car as a daily driver, on an 80 Mile commute, so a turbo, at this time, is out of the question!
You didn't post your age. I don't know if insurance is an issue for you. If you want preformance off the lot the GTS is a no brainer, I'm glad the guys here guided me in the right direction!
Hope I helped