Did some testing yesterday on PGL and I can say that there is no magic number as far as AA stats go. The idea simply remains to be that increasing either of the AA stats grants higher damage, however crossing any threshold does not give a sudden rise or bonus of any sort.
The following is my parse breakdowns versus the static Lv 54 Gigantoad spawn near Turning Leaf.
289 STR and 278 INT = 567 Total
http://i56.photobucket.com/albums/g1...-09_081904.jpg
286 STR and 288 INT = 574 Total
http://i56.photobucket.com/albums/g1...-09_080426.jpg
Granted the sample sizes are not large, but I was in a hurry and squeezed this in prior to a Moogle run. Even with this size I think it's safe to say that there is no bonus for having a stat simply pass the 280 mark. The only thing to take from OP it seems like is that stats do give increases up to 340.
EDIT: These tests were done entirely under the effect of Fists of Fire.
