personally i would get a gts. nothing against the GT but after spending the difference in price on upgrades you will only be pulling numbers close to that of a GTS. Plus i'd rather say i have the top of the line celica, than i have the bottom line. I dunno like if i were to get an rsx, i'd want a type s, if i were to get a civic, i would want a SI. Although i would take a base 350Z, but they all have the same engine
Celica gets good gas milage, so i don't see a problem spending the extra $$ on premium. Much better than paying for premiun and only getting 19-20 mpg (300zx NA almost got one). How much are you planning on spending? An important thing to think about is what you want your car to be. For me my car is my hobby, my friend, my outlet. I like looking at my car in the parking lot, i love to take it out just for random drives, when i'm angry i love to take it out and push its limits. I mean there are a lot of things to think about before buying a car.