Mazdaspeed Racing hart don't look good at all on a Mazda 3, the offset is too high so the wheel look too inside and they are 17", on the other side, the Mazdaspeed 6 wheels look amazing and fit perfectly. If you want to go with the Racing Hart you will have to buy spacers, at least 5 mm.
Mazdaspeed6 but paint them in glossy black.