I think that all the training/work/near death experiences that goku had as a kid should have made him WAY stronger because of all the stuff he went through, he took down an army for god sakes, and yet in the first episodes of DBZ he struggled against his brother.

Another good question would be: What would Nappa look like if he went super sayain(even though he died before he was able to obtain this ability its a good question to think about)

me and a few friends came to the conclusion that the sayain aura would be on top of his head(because hes bald)