If you're thinking of buying either "xoo Multiples" or "Yellow Magic Orchestra" then bear in mind that they're both available in different versions.
There's a 2CD version of YMO has both the original and US (remixed, different track lengths etc) versions.
There are 3 versions of xoo Multiples that I'm aware of - the original, the US version (the one that I have, which is a compilation of tracks from xoo Multiples and Solid State Survivor) and another version (UK? - a compilation of xoo Multiples and YMO).