Well, to be honest there is not a wide variety of brands around Rio (for a fair price, at least). You can find the major brands, though. Well, there is a good shop of second hand instruments where maybe you can find something different: (
http://www.promusic-rio.com.br/). You can find more variety in Sao Paulo, I guess...
I didn't pay attention to music stores in Bs As, when I was there. Are they good?