OK the 8800 GTX fits the Thermaltake Tsunami VA3000SNA, with modification. From what I can tell this case cannot take any dual slot video card without minor modification.
What I experienced is that there are plastic supports that run above the expansion slots which are normally between each board, but with a dual slot board its in the way and there is no way to get the back edge of the card in while its there.
What I did was cut the top edge of the piece of plastic with a small wire cutter, then i was able to bend it back and forth a few times until it snapped off, making room for the card.
Here you can see the purple plastic supports as well as the one I cut which is between the open pair of green clips on the right. In the picture it is pushed to one side as I began to bend it back and forth to snap it off.
In the next picture you can see the plastic piece gone and the card in place.
In regards to size I had no issues at all. There is plenty of room between the card and the HDD cage, and I was even able to leave my HDD in the top rack.