Hi Paul, Sanjay:
I do have the volume control on the Platinum DAC III, so I'm not using a pre-amp. The upsampling is 8X on 44.1 and 48 KHz signals. The upsampling can be enabled or disabled based on a toggle selector. I prefer the sound with the upsampler enabled, but this might be because I've always used some kind of upsampling on either the transport or DAC side.