Is the Nine Tails still stronger than the Eight Tails even though half of him was sealed away? I've not read the manga series, so the question may be quite basic. 

In an earlier discussion, it was said that the number of tails determines the power of the tailed beast. Since half the Nine-tail's chakra was sealed by the Fourth Hokage, does it mean that the Eight-tails now has more chakra than the Nine-tails?
It's not specified explicitly, but I think not.

Itachi told Kisame that the nine-tails had to be sealed last, because if it doesn't, the Gedo Mazo would be thrown out of balance, and break down. Akatsuki definitely knew about how the Kyuubi was sealed, because Tobi was there.


   In the manga, Naruto together with the Nine Tails managed to fire a bijuudama of equal scale to that of the Two, Three, Four, Five, Six and Seven tails combined.


From those I conclude that even after half of him was sealed away, the Nine Tails still has more power than the rest of the tailed beasts, if not combined!