well, XBOX360 is more mainly a game console, while a PC is more multi-function....
but I do think XBOX360 is more powerful than a $400 PC right now. XBOX360 runs at 3.2 GHz speed with 512 MBytes of Unified RAM with 10 MBytes of Embedded RAM with a 40 Gbytes HDD for $400.
If you bought a PC with motherboard that support 3.2 GHz speed, and a 3.2 GHZ CPU, with a 256 Mbytes Video Card, and another 256 Mbytes of main RAM, I believe it will cost more than XBOX360. Either way, a 3.2 GHz CPU for PC is different than a 3.2 GHZ for Video game console. Both are design differently for different reasons. One was design mainly for games while the other are more multi-function...