Do I need a sub?

Ok, found an absolute steal on a BIC AMERICA V1020 sub.

 A steal!!!

 My only quarrel is with my preamp, there is no sub hookup, so I will have to do the speaker wire to sub, and back to amplifier thing, which sucks.

i much prefer the rca from sub to preamp, but nope,.

is there an easier way........besides getting a new pre. My pre is wicked! McCormack LD-2 , a great pre!

First sub in 20 years.
first was a 12” cerwin vega front firing 
long times ago.

  Hoping this will add some low end.

 Even. My sanders sound pre does not have a sub iinput,
or my old onkyo p308.  
Such a shame, I. Have to do the wiring exchange for the sub.

 I very much like the rca automatic sub thing, but my gear won’t allow it.
and no I’m not changing, my stereo sounds amazing, and took me 35 years to get where I’m at these days.

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??