Disklavier

I'm thinking about upgrading my Mark III/DGC1B to the DKC-850 and wanted to confirm that the 850 would have better control over the loudness.  Right now, even with the loudness set to the lowest level, its still too loud for comfortable background music.
I also need to find where I can purchase this unit.  A couple of Yamaha dealers have not responded to me.  I plan to install this upgrade myself as it appears straight forward.
Thanks,

Ray