What’s the best rca “Y” adaptor?

I have a ARC SP-9 MKll Preamp with only one set of outputs and I’m thinking about adding a sub woofer or two.  I can’t go off of speaker cables because I have Acoustat  Model X’s and the have the Servo amps with three wires to the speaker, so I must pull off of the preamp.

I looked in the older posts and the newest one was from 2004, so what’s new in the “Y” Adaptor world?

Thanks in advance.

JD