Micro-what is more *advanced* about recent design tube amps? Are you referring to bigger power supplies and the latest generation of CJ output transformers or something else?
Although the best known upgrade were the proprietary Teflon capacitors, most of the improvements in CJ designs have been in power supply design. They improved the quality of the passive components used in the power supply, and changed some of the discrete regulator topologies. I have owned the ACT2 and ACT2 series 2 and the improvement in sound that a few changes operated has very large - and mainly in the sense Lloyd is looking for - purity of sound. As I am very curious and access to CJ boards is very good I studied very well both circuits.
Probably the output transformers of recent amplifier have also been upgraded - but I never learned about it.