I use the Viva solista and have to say it is the best amp I have had. Fast , transparent and neutral with real drive. Having said that, I am about to get rid of it, my wife hates it, to big, to black, runs to hot.
I had a Karan K180, which was'nt nearly as good, neutral, but lacked drive and dynamics.
I heard the LSA room at RMAF and was very impressed indeed, with the standard amp, the Signature and statement must be very good indeed.