I bought one of those YellowJacket AC splitters ($15 at my local hardware store) with the 2 ft cable and expanding one outlet to three. After disconnecting the single MC-0.5 magnetic waveguide that I previously had in the only unused AC outlet that is in parallel with the outlet that powers my HFC URH power conditioner, I plugged into it the splitter. I then stole 2 waveguides from the unused outlets of the power conditioner to fill the other 2 expansion slots in the splitter, along with the waveguide I disconnected. This made a huge difference in the magic midrange that HFC products improve, i.e. huge soundstage, more immediacy, transparency, speed, dynamics, detail, tactility, ease. So two conclusions: the use of a cabled splitter works as others here have posted, and the MC-0.5 makes a much greater difference upstream of the power conditioner than downstream.
So I was wondering: Has anyone daisy-chained splitters? I was thinking of using a splitter in the parallel AC outlet, into which I would plug in three more splitters of some configuration, giving a total of 9 outlets into which to place MC-0.5s. For the math wizzes out there, each added level would increase by a factor of 3 (i.e. cube) available AC outlets. I suppose there is a limit to this idea but wondering whether anyone else has thought of this or tried it.