it may be we are not on the same wavelength. What do you mean by "single line"? left audio out or right audio out and is this a speaker out connection or is it a sub-woofer out?
As for the "rca coax splitter", what are you trying to do there?
bought an rca coax splitter and 12 ft rca run for my receiver's subwoofer out. the back of the sub (mirage ss-1000) has L/R input so I split the single line. That's the way i've always been directed to do this.
Today at work I was extolling the virtues of Monoprice.com and the stuff i bought, but then someone asked why split it L/R? They didn't see any benefit. I got nothin for that one. Does anyone know a reason (technical or otherwise) why you'd split a mono signal into a L and R input?