hooking up subwoofer to 2 channel tube amp

I see.  So you are saying I need something like a spade plug at the base of the out and keep my banana plug into the terminal itself so there are actually 2 speakers (one main and a sub) attached to the same place?  Do I have that right?

You got it right!
https://ogrforum.ogaugerr.com/fileSendAction/fcType/0/fcOid/43524898376238682/filePointer/4352489837...
Any combination will work.

Check out REL subs.  They connect through the speaker outs on your amp but only augment the base without involving a crossover.

Thanks!  I was actually just looking at one.  I need to test them out, but a sealed sub seems like a better move for me than ported.  I don't want to bass to over power, just something to fill out the sound 

Imhififan, yes!  Perfect picture.

Keep in mind that some subs, including RELs, use the Neutrik Speakon connector for speaker-level inputs. Thus, you can't just use basic speaker wire. Other brands, such as Rythmik and KEF use regular 5-way binding posts. IMO, the KEF Q-series, sealed-box subs are sleepers and offer great bang for the buck.