>What is it about discrete Class A balanced amps that makes Aryas sound better?

Generally speaking....

Discrete amp topology: is generally more adept at passing spatial information in the music as compared to IC based amps - ie: HxWxD and positional information. They're also better with revealing trailing edges and minute nuances in music/vocals/instrumentation too. IC/THX-based amps tend to sound sort of unnatural, by not reveal spatial info as well as - especially soundstage depth - as well as "cut-off" trailing edges/nuances whose details make music sound much more natural and "real".

Class A bias/topology: Most amps are Class AB - meaning that one transistor may drive the " + " part of the musical waveform, while another may drive the " - " part of it. In between + and - , neither will be 100% accurate when they pass off the signal to the other. What this is called is "crossover distortion" - when there will be a distortion of the waveform as the signal goes from pos to neg and back again, and this is a major part of an amp's treble harshness. Class A amps don't have any crossover distortion whatsoever. They have their output transistors handle the whole waveform - they stay "always on" through the whole waveform up until the amp is turned off. As a result, they're smoother in the treble and midrange than most Class AB amps - unless the AB amps are biased deep into Class A. Another benefit of Class A "always on" operation, is that they pass along more current into the load (ie: the HP or speaker) - which accounts for their deeper, punchier, and more dynamic bass capabilities.

Balanced operation: Balanced amps simply offer more power for the same voltage. Plus, they'll be more resistant to noise across the board - as well as being resistant to EMI, RFI, and may also have better apparent stereo separation.

Sorry for the long post, but you can do some more reading on each italicized topic. I really couldn't make the connection that amps made any difference as long as they were powerful enough. That is, until I actually tried out several IC based amps and compared them with my cheaper discrete Class AB amps - then, the differences were really obvious. Then I found a used Class A amp for a reasonable price (Gustard H20), and I was floored - the bass was sooo deep, punchy, and dynamic - while the treble and mids were uber-natural and smooth. Of course it took me getting the revealing Arya before I even thought about trying out different amps. Hope this helps.....