Second sub connection

A basic question but then again basic is the limit of my audio knowledge. I currently have a Schiit Freya preamp with two rca outputs. One output is running a pair of tube amps the other was for an older Quad subwoofer with rca L and R inputs. I just purchased a second sub (svs pb2000) with the same inputs. I had a brief conversation with SVS and was told to run a pair of cables to each sub with splitters.
i have an old pair Radio Shack Y splitters male to female and could put one in each channel of the second output and run a pair of cables so each sub is getting a right and left feed.First...is that correct or should I run one sub only left and one only right?
Second...could I use different splitters on the sub end (dual male to one female) and run one cable each from the the preamp L and R to the subs.
The second application would save me some money on cables. I already have a pair of 12 foot cables that were to my first sub, the second sub would need a 22 foot run. So I thought if I took one of the 12 foot cables and patched it to a 10 foot cable I could run that to new second location if I were to split at the sub end. Not knowing the difference because of my current cables one is coded red for right and the other black for left (normal) so is that going to present an issue separating them. Don’t want to compromise on the connection to save money but I would like to understand better how this works.
Thanks for any responses that might shed some light 💡.
Dan