I do not agree with the Sakura helping him logic. First it's two on one for that matter all Gai has to do is open the eight gates kill A and have Sakura heal him. Second Sakura's a skilled medic but she's not going to make any difference is Gai opens all eight gates. Gai is going to die if he opens the last gate. A's natural speed and power I see as more then Gai's natural, and the lightning chakra I see exceeding it even more. Opening the Gates for Gai I believe is a must. If he does open all gates both shinobi are going to die.
One more thing the concept of being more powerful then a Kage when you open the Gates is literal, you're physical prowess May be above a shinobi who has the physical prowess of a shinobi. If Lee opened up all eight Gate I do not believe he could take down any of the Kage because of inexperience and superior intellegence on the Kage's part. The comparison was made to give a general understanding of the imense power the shinobi possesses when opening all eight Gates not that they'll automatically defeat any Kage they want if they decide to. In a battle, jutsu skill, intelect, a shinobi's emotion, their reason, and their overall skills in the shinobi arts decide a battle not always the powers one possesses.
