Like mix as well. We have natural wood crib, cherry stained rocker, off white changing table, dark brown almost black dresser in LOs room with green walls. I love the way it looks.
Yes I think espresso and white go together. Even if you look for an espresso dresser, you may have a hard time finding an exact match, so I think you'd be better off going with the contrasting pieces anyways.
What about the dressers from the same product line as the crib or at least same manufacturer? The colors should match at least. I personally like the furniture to match in color and design but thats personal preference
Re: white and brown
I think you could mix them--that would be a nice contrast! As long as you're not trying to match wood tones... I think that's difficult to do.
Good luck!