Just bought an old house, its American Walnut all over the main level. Need to rip off the old carpet off the two flights of stairs and upper level to hardwood. I need something to coordinate well but dont want to go with a darker wood like American Walnut...and we definitely want to go for something harder and of better quality.. Looking for ideas/advice if any of you mixed two different colors on different levels and how that worked out. Would love to see pictures.
And finally...if I absolutely have to go dark then I am looking for Brazilian Walnut. Anyone have experience with the broader 5 inch planks and any recommendation/warnings about any local hardwood stores to go to or stay away from!!!

American Walnut is beautiful. Might be a shame not to carry it on through, especially with a Brazilian specie...Sorry really didn't address your questions....just almost seems like a crime.

Thanks for your reply. Are you recommending I carry american walnut to the second floor? Or are you saying Brazilian walnut on second floor?
Any thoughts if Brazilian Teak might work well?

I don't think either Brazilian Walnut or Teak will even "blend" with American Walnut, completely different looks,( I'm going by the Bellawoods, I'm guessing that's what your referring to). Ofcoarse I'm guessing without seeing your layout...but I tend to like running the same wood throughout, ( American Walnut ). But that's just me..

Is your Walnut floor square edge flooring that was sanded and finished on site ? Or is it pre finished with micro bevels ? Your answer will shape my recommendations .

I agree with the other guys. I would use the same woods throughout. If you absolutely want something different I would do something light, as the other woods mentioned might look as if you tried to match the existing flooring but didn't. A lighter wood that would contrast great with American Walnut would be Maple.