AMD recently released their line of Radeon 6800 cards but they haven't released their enthusiasts SKUs in that line. Right now, you can grab the mid-range cards but will they be able to let loose their leader before NVIDIA?
Rumors of the NVIDIA GeForce GTX 580 can be found
at Nordic Hardware and NVIDIA's banking on giving the consumer a more powerful Fermi card. When the GTX 480 first debuted, they were a few CUDA cores short of the original specification but it looks like they are going to include the full 512 CUDA cores, up from 480.
Also, Nordic says that they've lowered power consumptions by 10-15%. which is good news as the GTX 480's a very power hungry card. Of course, you're going to get higher clock frequencies and such so all these improvements should make it the fastest single card solution if it's released this year.