Sorry, if anyone wants a "fast" answer, please get in touch with support@nuprimeaudio.com.
I visit this community site typically every week.
Evo DAC-2 is slightly warmer (which addressed the only criticism we have received about Evo DAC) and more detailed (the result of using better opamp) than Evo DAC.
To consider Evo-DAC + PRA-9X or Evo DAC-2 really depends on your requirement for preamp inputs.
Keep in mind that the improvement from Evo DAC-2 over Evo DAC is only incremental.
Likewise, Evo DAC-2 has a very good preamp section, similar to PRA-9X.
If you already have Evo DAC, then it is a no-brainer to just add PRA-9X.
Since you have Nuforce P20, and I assume that you don't have a world-class DAC, then definitely go with Evo DAC-2.