The Synergy IIi is a very fine preamp and would obviously work well with the Rowland amps.
I believe that most solid-state preamps don't sound stage as well and lack the musical timbre of tube preamps. The Synergy IIi is a rare exception. I own the Coherence II, which is the best preamp Rowland ever made, and it smokes the three tube preamps (CAT, Hovland and Jadis) I ran before it. The Synergy IIi is quite close to the Coherence II in performance.
I know nothing about the newer, cheaper Rowland preamps.
As for amps, you may want to consider some of the older Rowland amps on the used market (Model 6 monos or 8ti stereo). They are incredibly well built and I believe superior to the new budget / home theater-oriented amps (201, 501) that Rowland now sells.