Xbox 2 - Sheer power

CPU - Xenon's CPU has three 3.0 GHz PowerPC cores. Each core is capable of two instructions per cycle and has an L1 cache with 32 KB for data and 32 KB for instructions. The three cores share 1 MB of L2 cache. Alpha 2 developer kits currently have two cores instead of three.

Also,

GPU - Xenon's GPU is a generation beyond the ATI X800. Its clock speed is 500 MHz and it supports Shader 3.0. Developers are currently working with an alpha 2 GPU. Beta GPU units are expected by May and the final GPU is slated for a summer release. The final GPU will be more powerful than anything on the market today; in game terms, it would handle a game like Half-Life 2 with ease.

thanks to http://arstechnica.com