I probably used incorrect terminology. By speaker line level, I was referring to the amplifier output to the speaker driver. I don't really know why I call them that other than that's what one of my subs calls them. I have not heard of a sub that had R/L RCA. All I've seen is a mono RCA and then the R/L speaker inputs with outputs for running a sub in between the amp and the speakers.

Thanks for the clarification.