jerryg123,
There is just one verson of AGD (assuming you heard the latest 2nd version) and only one version of the Atmas.......but there are tons of versions of the Purifi based amps and they all sound different from each other. So, which version (which discrete op amp, which regulators, dual mono or single power supply, quality of output jacks, etc.) by what company did you hear? As I mentioned before you can read on 10 Audio.com that my modded $1600 Purifi based VTV amp was preferred greatly to a NAD amp with a stock Purifi......
There is also a newer higher powered module from Purifi that has been for sale for some months now and it is supposed to sound better than the original......yet, they both are PURIFI modules.......again, what did you hear?