M.-
It really depends on how many teeth your child has, and if he has any issues with texture. The more teeth he has, the more able he will be to handle chunkier foods - does he ever gag or choke on the stage 2 foods that he eats now? If not, and as long as he has more than 4 or 5 teeth, he should be able to handle the stage three stuff. There are many more larger chunks that require teeth, even molars, to appropriately chew pieces of food that he might otherwise choke on.
If you think he is ready, buy a jar or two of the stage three and see if he handles it well. My daughter had 10 teeth by the time she was 10 months old, and totally skipped over the stage three and went right into soft table foods.