The HA-3A turned out really great with the auteurs, in a lot of ways it's the most practical of the Cayin all tube/transformer based amps in that it works with most headphones except for the very most power hungry ones, and even then it will drive them to a decent volume. Being small it can fit in many more places than the other units, and it also has a sound that hits the perfect sweet spot between tube euphony and extension and control. It's also the quietest amp of the three - which for those new to tube amps is a good place to start, not that I personally find the other units noisy at all, but with lower power the innate issues of tubes may not be as much of an issue.
I recorded a video yesterday on the 3A as well as a comparison of the entire line-up that I hope to have out in the next couple weeks. We have 5 units left from the first batch, and more will be on the way in the next month or so.