You can't just crank the ISO and get clean images. When used properly this camera is capable of very clean high ISO images relative to other APS-C cameras, and some full frame sensors. The camera is not going to take a great picture itself. It needs a skilled operator to extract the most from a given scene. Since there is more data held in highlights as opposed to shadows, it is advisable to expose to the right, or expose your picture close to the point of overexposure in order to gather the cleanest data to make your image. Pulling the exposure up in post in an underexposed photo will always result in more noise because there is less data in shadows, so the imaging software has less data to work with to retrieve details.
Read on exposing to the right, work on your technique to maximize the amount of data collected in a given scene and you will be on your way to collecting high ISO images that are clean.
Some examples...
ISO 2000
500px / Photo "Rockwellian Capture" by Robbie Vize
ISO 1250
500px / Photo "Spin" by Robbie Vize
ISO 2500
500px / Photo "Asleep at the art crawl." by Robbie Vize
(notice how much more noise there is visible in the darker areas, and how less noise is visible in the lighter areas? There is also much more detail in the highlights.
ISO 2000
500px / Photo "Gunner" by Robbie Vize
ISO 3200
500px / Photo "Gunner" by Robbie Vize
In all of the photos, notice that the clean details are in the brighter parts of the photos, along with the highlights that occur in the darker areas.