also, case in point, theres an eppisode where gotenks is fused in the bathtub, and goku scares the crap out of him by going ssj1 >_>
and thanks for proving my point alea, if goku could only beat fat buu at ssj3, and kid buu beat the crap out of fat buu, since goku actually held his ground against kid buu, wouldnt it be safe to assume he is the strongest?
also, the kai training didnt "multiply" gohans power, it unlocked his fighting potential, the same way as the old namek did. thus eliminating the lack of training. since training realises someones potential, if it becomes unlocked, the training is not needed.