the xbox would need more power and be harder to emulate?
sorry but i totally agree with Katsuya, in all reality it is just a pc in a box, it uses an intel x86 processor, an nvidia graphics card n god knows what other pc hardware.
to be honest i doubt much actual emulation is needed for most of the system, granted you will need to convert some to make it more native due to the XBox's own executable format etc, but everything else will use x86 commands same as a pc.
but to be honest, any games on the xbox that are on the pc, are much better on the pc, only the crap titles on the xbox havent been released on the pc.