I have been using the Bryston SP-1 for several years as my sole pre/pro. I use the SP-1 as the DAC for all of the digital sources in my system (both 2-channel and surround processing), as well as the analog preamp for my vinyl playback system (see system link for description of my system). I think the quality of the DAC is excellent -- it was a clear improvement over the DAC in my Rega Planet CD player.
The SP-1.7 is essentially the same unit as the SP-1, except for the inclusion of additional channels of surround processing, analog inputs for SACD or DVD-A, and the inclusion of Dolby Pro-Logic 2. Both the SP-1 and the 1.7 use the analog circuitry from the Bryston BP-25 preamp.
There are better stand-alone DAC units on the market (such as the Chord DAC-64), but you will have to spend a lot more money to do much better (and none come with Bryston's 20-year unconditional warranty). I cannot comment on the quality of the Krell unit you mention, siuce I have no direct experience with it. What I can say, however, is that the Bryston SP-1 and 1.7 pre/pros offer very high value / sound quality for the money.
The SP-1.7 is essentially the same unit as the SP-1, except for the inclusion of additional channels of surround processing, analog inputs for SACD or DVD-A, and the inclusion of Dolby Pro-Logic 2. Both the SP-1 and the 1.7 use the analog circuitry from the Bryston BP-25 preamp.
There are better stand-alone DAC units on the market (such as the Chord DAC-64), but you will have to spend a lot more money to do much better (and none come with Bryston's 20-year unconditional warranty). I cannot comment on the quality of the Krell unit you mention, siuce I have no direct experience with it. What I can say, however, is that the Bryston SP-1 and 1.7 pre/pros offer very high value / sound quality for the money.