snowkatt: other then the 32 x ( optional) and the new 3DS i cant think of any update that actually changes a console's performance
Well, there is:
The Nintendo DSi, I believe, is more powerful than the original DS, at least in terms of amount of RAM.
The Game Boy Color, which is really an updated Game Boy (as apposed to the Game Boy Advance, which is new hardware), has a CPU 2x as fast as the original Game Boy CPU, I believe. (Note that many games were released that would play on the original GB, but could take advantage of GBC specific features like color; Pokemon Gold and Silver (not Crystal) are examples of this.) GBC only games, if you tried to play them on an older Game Boy, would typically display a screen with a message saying something to the effect of "You need a GBC to play this game". For example, Pokemon Crystal will display a screen with Crystal spelled out in Unown, while the Wizardry 1 adaptation shows Murphy's Ghost on a monochrome Game Boy.
The Nintendo 64 got a RAM expansion, which was required for a few games (Donkey Kong 64 and Zelda: Majora's Mask are the two examples that come to mind).
I believe the PC Engine could be updated with cards. Castlevania: Rondo of Blood required such an update, or the game wouldn't run; instead, you would be sent into a cartoony stage, and at the end of the stage, the game would display a message to the effect of "you need to upgrade to play this game". I believe the PSP version included this stage as a secret called "Stage X".