The Crescendo is a lovely preamp, and a pleasure to use via wi-fi. Its resolving and extended, and offers a wonderful midrange density so often lacking is solid state components. Its internal dac is very, very good. I've not used the Concerto amp, but have used Viola's other amps. The Forte' monoblocs drove Hansen Princes wonderfully, and their Bravo and Symphony amps driving the Ocean Way 'monitors' was simply outrageous, in a good way. Paul Jayson and Steve Ffrench are a pleasure to deal with.
-Paul
Waveform Fidelity / Kaplan Cable