Don't see a flywheel specific for the 2012 on fswerks, though there is one for the mtx75. Not sure if it will match the GDI, though.
Personally, I go brakes > tires/suspension > drivetrain, just so I have the tools to fully exploit any power gains (and I prefer handling to speed). But with whats out now for the 2012, the power increase isn't going to overpower the current chassis setup. That being said, if you cruise through the dyno thread, you should get a good idea what kind of gains to expect with that setup, which will be noticable.