I can only be so specific. Yes, I've heard in my room(side by side) all but the new Bal Canto Ref 500s and the top Rowland 312s. There is just a staging,imagery that the Spectron produces that the others can't match. Yes, the A. Research 150.2, CIA D200s,W4S SX 500s and even the Rowland 501s sounded very good.I've had all the digital amps as I'm a believer in them. Had one since the B. Canto 2000.2. They're all great amps but, the Spectron is special! Hard to put to words really. I'm talking about the stereo amp with no V-cap or Bybee mods too. If imagery is important then the Spectron is tops. If not, then a lot of amps can fill that space. This all coming from a die hard SET amp guy. I have three all together different systems.