But the bitrate on 9477 is not low. Currently, it has 2-3 times as much bitrate as normal, because the space is being saved for the next HD channel additions.
To repeat, if 9477 looks grainy, then either your set needs to be adjusted (as Tom Bombadil mentioned), or you are sitting too close, or you are looking for artifacts rather than watching the program. 9477 is sitting in a half-empty transponder, so it gets quite a bit more bitrate (at the moment) than most other channels. There should not be any problems with that channel.
Just a speculation -
If the cable HD picture was actually too soft, then the picture might have looked better with the shaprness control turned up high. At high resolutions, the pixels are smaller, and so the artifical sharpening looks like added detail.
But, if the set is then connected to a source with more detail, then the added sharpening is too much, and looks "rough" ("grainy" ??).
So, you might try turning down the sharpness setting.
PS Lastly, odd effects can be caused by a loose cable connection anywhere along the path, and also by ground loops and other grounding problems.