Need some help with wiring. I'm running a SMSL AD18 with ELAC B6 and dual R-12SW's.

I am currently using this cable to the subs LFE rca output into the input of SMSL AD18 along with speaker wire to my ELAC B6's. This feels wrong for some reason and I just want to learn the proper way of wiring this setup. Everything works at the moment but I feel like I did something wrong.

I've read that you can use the 3.5 coaxial output of the SMSL AD18 as the sub output using this cable. If I wanted to use dual subs, could I just use this along with 2 of the cables above?

Is there a benefit in running it this way vs what I have now?