I like Franke sinks. I am very happy with mine.
Showroom is down on 9 de Julio y Santa fe.
http://www.franke.com/countries/ar/es/home.html
I would recommend FV for grifferia, as its a good balance between quality and price. You can certainly spend a lot more, and you can even buy 100% plastic grifferia for a few pesos at Easy, but the FV stuff, especially its midrange to higher quality products, are pretty well made, and replacement parts are easy to get everywhere and likely to be in stock years from now.
http://www.fvsa.com/
Everybody carries it, from the most expensive shop to the corner plumbing supply.
Blaisten is good to see the range of whats available- and they have good stock-
but you should also go across the street to Barugel Azulay which is more high end- Blaisten is where the contractors shop for the cheap stuff, Barugel is where the decorators shop for the fancy stuff. If you have been dreaming all your life about a $3000 Phillipe Starcke bathtub- well, there you go.
There is an entire granite countertop and tile neighborhood over in Nunez, a block south of Libertador , near the Barugel store there.
Walk around and see a bunch of stores with a very wide range of stone and tile selections.
Stone is quite cheap in Argentina- its a good value. A lot of the stone is South American, although they certainly stock Indian and other imported stuff as well.
If you are interested, near the Pulgas on Cordoba, there are several stores with lots of new old stock in ceramic tile, lots of 50's and 60's patterns, including things like built in ceramic soap dishes and towel holders.