I have a background in selling and installing high end leather aircraft interiors - I tend to favor a soft, damp terrycloth towel. We see a lot of people putting all kinds of stuff on seat leather with detrimental results. Car seat leather, like that in the GT, requires no conditioner or "stuff" to keep it nice. Essentially, it's a myth that products like conditioners will help your seats, extend the life, or make them supple. More likely, you'll coat them with something that will make them slick, build up or discolor them.
If they were natural leather, I might suggest otherwise. The leather in your car has a topcoat that is, basically, paint. Unlike the exterior, waxing it doesn't make it more attractive imho.