Why not check out some of the local gyms? Ask them where they buy their equipment? Regarding used equipment, I have a feeling if you asked them what they do with their old equipment, you'd get a puzzled look.
Good one rellosk!
My experience is that they leave their old equipment standing in the gym - with a piece of paper (sometimes) on it saying it does not work.
That said I see that most of the bigger supermarket centers (Sirena/Plaza Lama Etc.) have a rather decent selection of new stuff.