dacs as preamps ?

Generally yes, a preamp in the chain is much better... but I am mightily impressed by the implementation in the Berkeley Alpha DAC.

The Benchmark DAC 1-Pre has a lot of fans. It's generally describes as very transparent, though many listeners find it "lean" sounding. I used one for several years and I'd agree with both assessments. At the end of the day, it's probably a fair bit of personal taste and somewhat system dependent.

Marty

Depends on the voltage and output impedance of your DAC. If you use something like the MSB Platinum, which can output 7.5V rms into 50 Ohms and your amp has sensitivity of 1.5V or less and 45K ohm or higher, then it should not sound lean. In fact, with high voltage DAC's like MSB the preamp will distort when fed such a signal. Passive is the way to go for a DAC like MSB.