I have heard the Oppo BDP-105 stock and for the price you are paying for it, it is an excellent product. You get a whole lot for the cost. That being said, there are definitely better DACs out there. I have completely rebuilt the analog and power supply sections of an Emotiva XDA-2 dac. It uses an Analog Devices AD1955 dac chip and the I/V stage is interesting in that it is an "active" I/V stage. This means that it presents 4 volts DC on the -input- of the I/V op amps. The power supply has to be able to supply constant current to this section (very much like a Class A stage). I have made this Emotiva beat the crap out of the Oppo. The Oppo 105 is no slouch in the power supply department, but overall design and capacitor choice, as well as choice of op amps, definitely affect sound quality.
On the other hand, my Krell S-1200 pretty much beats the Oppo - and it uses the same Sabre 9018 DAC chip. The focus is on using a TCXO clock oscillator as well as extremely well designed power supply and analog circuits. I have not really put my Emotiva up against the Krell yet, but I suspect it will be close.
The choice of Sabre dac here really doesn't have much to do with it. That being said, I remember hearing and reading in early years that the Sabre DAC was very hard to work with -- you really had to design the circuit to work well with the electrical properties of the Sabre. I don't know if this is true anymore or just heresy, but it's something to remember.