The renders look really nice. I agree with the others that increasing the samples will make it look cleaner but renders will take long time. I can't see the noise you talked about in the last ball render. Perhaps you're talking about the slight blurr (fuzziness) of the objects. If so, you can fix that by adjusting the filter in your render settings (quality tab I think). Change it to something like "Mitchell" which will make the render look more sharp. Since you don't have tight details or textures it should be okay to use Mitchell or even Lancoz for the filter setting. Just depends on what kind of look you want.