I just jumped into the way-back machine and read about the Nintendo/Miyamoto press conference when the GameCube was first unveiled.
To smack down the theoretical PS2 power, Miyamoto said that anytime you add an effect, polygon numbers basically cut in half... i.e. 20 million a second can easily become 10 million.
Until further notice, I think I am calling "wait and see" on the Revo GPU until there is actual data to go on. 2x the polygons don’t mean 2x the graphics... according to Miyamoto it would really only mean one more effect can be added.
And even the low-end graphic chips are beasts compared to the GPU in GameCube now... Nintendo would be seriously lowballing themselves (and us) if that's all they decided to go with.
The ATI x300 card can be bought for $40. Wholesale would be dirt cheap... and at 800x600 resolutions it does respectably on even Half-Life 2 and Doom 3 benchmarks (within 30-60 frames per second.)
Also, doubling the clock rate of the GPU (which IGN's sources claimed it does) in this case is more dramatic than it sounds. Flipper was what, 162MHz? The X300 has a core speed of 325MHz. You do the math... that's exactly 2x the Flipper. As KDR mentioned, there's more to it than clock speed that makes it more than twice as fast, though. (Pipelines, fillrate, etc.)
So if "Hollywood" is even anything like the cheap-ass x300, we're still dealing with something pretty ample for standard def.