The hotel is nice, with large rooms, and it is very cheap: just 65 Euro for a double room with private bathroom in a 3-star hotel, breakfast included.
The worst part is the surroundings: the view from the room was on the site of a demolished building, and the neighbourhood did not seem the best kept in the city. But I always felt safe, and it is just a 10-minute walk to Brussels South railway station.
Chaussee de Mons is also known as Bergensesteenweg (for Dutch speakers).