Antonio: I've been very happy with the cooler. Because of the warm temperatures here, I didn't actually lower my CPU temps much, but when I'm gaming the temperatures don't go near as high. I can't give you specifics because I can't remember what my temperatures were with the stock fan, but if you're in a very warm/hot climate, you should see a big drop in max temps.
This cooler probably has the best bang for the buck if you're looking for something cheap.
The single included fan has been great for me (my Antec 300 case also has good airflow). I have this cooler on a Intel Core i7 2600K running at 4.5GHz. In the past I have run similar "tower" style heatsinks with 2 fans and if you plan to run with two fans I suggest the following I learned from my experience:
Run 2 of the same fan OR 2 fans that have similar RPM and Airflow specs.
1)Different airflow rates can affect performance in different ways. Using 2 fans in a push/pull, a higher flow/volume push fan will lead to increased pressure between the heatsinks plates. Using a higher flow/volume pull fan will cause a vacuum between the plates. Neither of these will give a major impact to performance but will result in the pressure trying to equalize by escaping in/out through any gaps around the fan. For the maximum airflow across the plates (and maximum cooling) both fans should move the same volume of air (CFM).
2)Different fan RPMs can cause the same kinds of problems mentioned above (since they will most likely move different volumes of air since they are the same size fan) but can also cause a buffeting noise that will vary in volume depending on several factors but can be quite annoying.
So if you get a 2nd fan, but the same model fan from CoolerMaster, or better yet get 2 new fans to use that are higher quality/higher CFM. When you buy this cooler, you are paying for the heatpipes and cooling fins, the included fan is fine but far from great. I feel that if you really need a 2nd fan, you are much better off with a higher quality aftermarket fan.