This is too low, if it were releasing last year it would be easier to swallow, but in 2012, with PS4/XB3 coming in 18-30months, I think there just isn't enough of a lead to give it a real chance...
Wasn't there some sort of surprising bump in performance between these two kits? chopping up a 640sp chip would be something they would plan from the get go, so I am not sure why they wouldn't go with a 480sp chip, as AMD has plenty to choose from... luckily it's speculation, but now your 640sp @ 600mhz (768GFLOPs) sounds like heaven... Damn you BG.
Also if Oban rumor is the Wii U CPU, that means it has dropped from 45nm to 32nm... being a SoC btw isn't surprising at all, seeing how well it worked for 360s.
If rumours are correct the final GPU has dedicated hardware too assist the ALU's with some intensive tasks (lighting perhaps?).