Gaara could take out the strongest Chuunins with ease I bet. Judging on his last fight in the manga... he has a lot of cool new sand Jutsu's. Him and Neji are main characters in a way, cause they haven't been dropped yet, and are still involved in the current arc.

The Manga made Haku out to be so strong, what with what Kakashi said as well, but yeah... I doubt Haku was really THAT great. He had the Ice Mirror Jutsu... but his Taijustu was just crap, plus, he almost got smoked by Naruto's shuriken.

Chuunin wise, the show has to release some more. They either focus on purely Gennin's, or the extreme Jounin/Sennin/Hokage type battles. What do the 4 sound nin qualify as? I mean, they needed curse seal level 4 to beat 2 Jounin's low on Chakra.