Naruto just completed an A-rank mission, which only given to Jounins. Completing it means he's qualify for a jounin.

He himself already possess alot of chakra as a genin (even more than a normal chuunin)... He only needed A BIT of Kyuubi's chakra to defeat Gaara... Imagine how strong he would be if he uses all of Kyuubi's chakra. I bet he can even put a good fight with the 3rd Hokage (if he doesn't use that Death Demon Technique) if he max out his chakra.