If you want to buy one card and be sure it'll be the last one (for that camera and for a couple years to come), go with the SanDisk Extreme Pro HD Video.
Its expensive but that card is a monster; having a 95mb/s reading speed and 90mb/s writing speed; miles away from what you already have.
I had buffering issues on my D7000 because I used Class 6 cards. With this card, the buffer empties itself faster then the camera can try to load it.
Lifetime warranty on all SanDisk products also.
I just bought two more from a guy in Taiwan for $26 each for 32gb cards. He swears they're genuine. But i'll wait to make some tests before spreading the info. If its true, I will most likely buy all he have and resell them locally. They're 129 on B&H's website. I dont give it too much hope, because the price difference is kinda fishy, but he sold me legit stuff before so i'm gonna give him the benefit of the doubt. He promised to refund if they're not genuine so I had nothing to lose.