O.K. here are some examples: Shot @ ISO 3200 no noise reduction in post-processing.
This first one is the overall scene no noise reduction in ACR and set to low in camera. The raw file was converted in ACR and the output is 11mp:
This is a 100% crop of the 11mp RAW output (size reduced in ACR)
This is a 100% crop of the full size RAW file:
This is a 100% crop of the full size Jpeg (24mp):
This is a 100% crop of the smaller Jpeg- reduced in camera to 13mp:
In a nutshell: the way forward IMHO is to shoot in RAW and reduce the file size in ACR. Don't forget no noise reduction was used! Jpegs with the A900 and high ISO are way too mushy. The A900 is also not really meant to be used in Jpeg.