Do I need a sub?

Yes.This is what I use:https://www.audioadvisor.com/prodinfo.asp?number=AQM22FHRD
They are very well made and snug fitting.

This works how?

two rca into sub, and a single rca into the preamp white pre out??

Amp output red and white both into the audioadvosir connector
and into the single rca of the sub?

@jtcf ,

main out rca’s from preamp into the audioquest hard Y adapter..then into the single rca input of the sub?

this is all?

 How will this hookup remove the low frequencies from the main towers,???

would it sound better to just use the speaker wire hookup style, which will actually remove the low frequencies from the towers?

or will hooking up with the hard Y adapter also remove the low frequencies from the towers?

 Thank you , in advance for all your time guys.

Get a adapter w two male 1 female , plug adapter in back of main out of preamp, then run single shielded rca to sub?

easier this way? this will just dump everything over a certain freq to sub?

 Or use the speaker terminals which will remove the low freq going to the speakers (towers) and allow a little louder volume,by not sending lower freq to the smalldual 6” woofers???