My favorite coffee is sold at an arabic deli called Damasco at Scalabrini Ortiz 1283 (about 1.5 blocks down from Cordoba heading towards Santa Fe). It's really pretty damn good. Definitely strong. I think the price is somewhere around $82/kilo now. They sell beans or will grind it for you. I have a drip coffee maker at home and ask them to grind it grueso (3.5) or otherwise you'll end up with a fine espresso grind.
ETA: No clue what kind of roast it is, though it is very strong. Never asked...