Well, it would seem that as no-one is porting MESS to the XBox
(which is a real shame as it would solve Atari 7800, Acorn BBC, Amstrad CPC and Spectrum in one go) its best for now to either run Linux on the X Box and run emulators for that OS.
Or go crazy
and run some of the most ancient Speccy and Amstrad DOS emulators via DosXBox V3! That cant be quick mind, that and you need a keyboard.
Still, as I dont own an X Box its all academic for me
but I can tell you I wont be convinced to change that situation till these classic 8 bit computers are emulated!