If you see the slide, you can see that the geometry power is increased by 60% ...
Or this is my mind :
6800 Go : 12*330 --> 3960Gpx/s
6800 Ultra : 12*450 --> 5400Gpx/s
7800 : 16*400 --> 6400Gpx/s
7800 : 24*400 --> 9600Gpx/s
Now little mathematics :
6800Go Vs 7800 (16*400) --> 6400 / 3960 -->
1.61
6800Go Ultra Vs 7800 (16*400) --> 6400 / 5400 --> 1.18
6800Go Vs 7800 (24*400) --> 9600/ 3960 --> 2.42
6800Go Ultra Vs 7800 (24*400) --> 9600 / 5400 --> 1.77
I think that the slide is about the 6800Go v2 and not the Ultra. But with 400Mhz, it might be have the same TDP than the Ultra ... Or maybe the same that the ATI (it would be better, because i will able to put a 7800 in my 9860

)