Am I done yet? LOL

@traudio I can of course not put myself in your shoes, but you’re listening room is not small. Maybe you can put the second sub for next to your record cabinet, to the right of it, at a nice diagonal from your existing sub in the front left corner?

Another approach could be to sell the sub you have and buy two identical subs with slightly smaller form factors, if you think that the size of the existing one would be too much for a second sub deeper in the room. 

Just tossing out some ideas myself. :-)

@bimmerlover 
Beside the record rack was considered, but on the right it would block the door to the rest of the basement. On the left you would trip over it entering the room. Maybe behind the couch or on the wall behind the couch and to the right (don't want to be tripping over cords). 
I wish I would have installed more outlets in the room. 
2 of the Revolution 3000 subs might work, but unfortunately they came out right after I bought the single 5000. 

The Accuphase dose have a very sweet sound …it is so me…but…I can see

Others preferring more bright.  I’ve heard that esoteric is more “clinical”?

👍

Often times bass response issues are because of room nodes which can be corrected by dialing in the peaks in the response. 

Agree with @jrareform you may be sitting in a null. Bass is tricky and if you have yet to crawl on your floor (military crawl), you will know what you are missing if and when you find it.

You may want to start with placing your speakers straight ahead (no toe-in).

Not knowing what dampening material is on your first reflection point, but 4-inch would be recommended- preferably with Owens-Corning 703- and not foam or most of what one gets from GK or ATS and others.

You may also want to try the diffusers you have on the back wall and place them at the first reflection point, or just underneath your current first reflection material.