"So the DAC1 and the DAC1 Pre sound similar enough so that any comparisons between the DAC1 and Bel Canto also applies to the DAC1 Pre?"
The original DAC1 uses NE5532 op-amps in input and output stages. The DAC1 USB uses the LM4562 in the output stages. The DAC1 Pre uses LM4562 throughout. It stands to reason that these differences might result in a different sound. I recently replaced my DAC1 with a DAC1 Pre and did a quick and admittedly unscientific A/B listening comparison before selling the DAC1. FWIW, I felt I could hear very subtle differences, but both sounded superb and really much more similar than different.