The Helios mains cable into the block and then mains, as these Styx blocks don’t have there own mains cable.
If you’ve got really good kit and of a certain quality where small changes in speaker wires etc can do good things, then I cannot underestimate what these cables could do. If speaker wires don’t make much of a difference, maybe don’t bother. I was put off my their shear size but hearing what they do I can put up with it. It’s very much worth a free trial and home demo if you think it might benefit.