In the latest edition of hifi choice, the K3 was described as having high frequencies that time beautifully, and combined with it's punchy nature, means that it's fun with rock music.
They also comment that there are likely to be real sonic benefits to either version of the new Active-K module, which should be available in 2016.
Epos have taken quite some time to bring this active module to market, I remember being interested in this back in the summer of 2014, but I could not wait any longer. I still think it represents an obvious upgrade path if you are patient enough to wait.