This was some years ago when I listened to them but I once drove from Milwaukee to the Twin Cities to hear a pair of Vienna Acoustics Mahlers at a brick and mortar store. They were being driven by a pr. of big VTL monoblock amps (can't remember which ones, but not the Siegfrieds). To be honest, I don't know if it was the speakers or the power amps, but I was not overly impressed. I do remember it sounding congested. I listened for about an hour with a wide range of music I brought along. IMO, the Atma-Sphere amps are the clear winners. They are super fast, extremely clear, have unbelieveable bass response, and the list just goes on and on. They do have their drawbacks, those being they require a one hour warm-up to sound proper and they put off tremendous amounts of heat.