Raquel is correct. I asked JRDG about the Concerto and Synergy IIi and was told that the Synergy IIi would be slightly better because of the separate power supply, slightly quieter background I believe is what they said; but I believe you would be splitting hairs.
Personally I wouldn't hesitate to purchase the Concerto if interested in a Rowland preamp.
Personally I wouldn't hesitate to purchase the Concerto if interested in a Rowland preamp.