As far as the G6 goes the newer the better. There were some issues with the latter models that have been addressed. Yes, get the GT if you can.
I know its a hard call between the G6 and the Mazda 6 since I owned both, you'll like the G6.
I know its a hard call between the G6 and the Mazda 6 since I owned both, you'll like the G6.