I also have an "LPA-S600NCX" stereo power amplifier and wanted to compare the two concepts. I really struggle to determine if there is a repeatable difference between the two amplifiers. On certain tracks I feel that the Purifi is slightly more relaxed & natural and on others feel that the Hypex is a bit punchier in the bass. However, I am not confident that these subjective observations are repeatable. Both amplifiers are neutral (in a positive way), musical & silent. The one noticeable / repeatable difference is that the Purifi is cooler to the touch. Save a bit of money and buy the Hypex ncx? You cannot go wrong with either - both are exceptional amplifiers!