How do I know if I need a sub woofer?

I listen at low volumes late at night---if I want a little more bass, I use the loudness on my integrated. I will say that I did have a REL sub and sold it since I didn't use most of the time. But now I miss it. 

How do I know if I need a sub woofer?

   Only you can answer that.  Do you feel like you're missing something?  Do you live in a space where you won't bother/intrude on neighbors?  I noticed a lot of responses on what equipment to buy, but that's not what you are asking.

Asked another way…. How do l know what l need?
 

In retail the worst thing is to have a buyer who doesn’t know what he/she wants.

If there is a dishonest seller, he will convince them of what they think they need.

If the retailer is honest, he may well have a head banging/nightmare experience.

The same thing can sadly apply in real life situations/relationships.

If you crank something like- Welcome to the Machine, and the bones in your ears don't vibrate, you need a subwoofer. Need is subjective so this may or not pertain to you.

Did we figure it out yet?

If not I will reiterate. Sound meter app + streamed white noise will inform you for certain.