Well, it all depends on the Pokemon you have. Most likely, you may have a fighting-type that's much better in Atk than SpAtk, then all you need is a good Atk IV; SpAtk IV won't be much use unless you want to use special-category moves; but, it's wiser to stick with it's stronger stat since you only need to worry about one if you consider EV training.
However, if you have a fighting-type that's better in SpAtk, such as Lucario (even if it's not by much), it's better to have a higher SpAtk IV, unless you want to use physical-category moves. The only fighting Pokemon that is significantly better in SpAtk than Atk is Keldeo; but since you're breeding, you won't encounter this problem.
So, whatever fighting Pokemon you have should be fine, and it's SpAtk will not affect the performance of the Pokemon. Just choose physical moves over special moves, and you'll have one heck of a Pokemon.
Hope I helped! :)