Sorry -looks like the X2 is a new architecture across the board. Developers got modfied macs as their dev platform, and I *think* it was based around a powerPC CPU (as made by IBM for Apple). The Xbox is a pretty standard PC/Intel architecture.
So, swapping the DVD drive for one of the new BluRay drives might be an option, but the CPU swap is completely out. My guess is that (via hardware emulation) the X2 will be able to play Xbox games (they'd shoot themselves in the foot if this wasn't the case), but not vice versa.
BUT - the long asked for PS2 emulator might be a possibilty on the newer hardware
