Don't listen to zero, he obviously knows nothing about the tuner scene.
To be honest, it's not the best choice. For starters it is a naturally aspirated motor, meaning it doesn't have a turbo or supercharger which is called forced induction.. Another problem is that it is FWD, which isn't preferred if racing if you have to start off the line fast.
So, if you have the ability to look for a better car I would look for a RWD or AWD car with a turbo (simply because the engine would have stronger internals to put more power into it)
But the good thing about the tuner scene is, if you want to do something with your car you can do it. (to a certain extent at least, it really depends on how much cash you got to spend).
If you got the cash take the mazda 6 and make it your own, if not, I would find another car.