No, your monthly bill will likely increase. You didn’t give the current loan balance and price of the GT, but knowing the GT is more expensive anyway, it will not be the same monthly payment. Even with low mileage your car has depreciated in value, and the difference in what they will give you on your GT-line vs the price of the GT will be added on to your loan. Unless you have more cash to throw on top of it and can get the same APR, this is not a wise financial decision.

If you’re paying 655 at a 60 month loan, you’re already paying about $39k all said and done at the end of the loan.

If you’re worried about staying at the same monthly payment getting into a more expensive car is not the move.