I agree Rosewood has a really nice balance. Warm yet snappy, kind of like Koa. I like Mahogany too, but not so much on large bodies (i.e. Concert bodies), as they already generally have a tendancy to be bass heavy, the spruce are a bit brighter, and are better on those. The best tone I have ever heard was a hand built maple-top, which you don't see often. It was a medium sized dreadnought, and had a wicked snappy percussive sound, which really lent to a nice bright finger-picking high-end with lots of good upper harmonics, and absolutely no mud in the bottom end.