The wii has a small amount of differences from the GC that make games that use all of the features of it more demanding than games that use all of the features of the GC, but there shouldn't be much of a difference between the two platforms. But, Xenoblade, if I remember correctly, is a very demanding game. I'm not sure whether or not you'd be able to play it.
in a perfect world we would all be piles of sand with no ability to form coherent bodies of body
