Right. Well, if going out on the market and buying 2, 3, or 4 subs to bring them home and compare them was an option, I would have done that. Unfortunately, I don't have that luxury.
No one has that luxury.
Im pretty active on AVS...except for the speaker threads, even though I've been dealing with speakers personally and professionally for 55 years.
The reason for that is that all those "what should I buy" threads come down to objective opinions, and then ramble on forever.
I used to tell my customers to buy whatever strikes their fancy, wouldn't even get into endless hours of comparing specs and features.
Whatever they bought from the shops I was at was quality equipment.
Like TLS Guy just said, you are making a ten course meal out of this.
Just buy a sub.All that were suggested are good designs and are good quality. Your room will determine the sound.
If I were you, I would dump your whole system and start over...your AVR is old and a weak one at that, and your speakers are bargain level entry models.
If you are unhappy with whatever sub you buy, you have to look at the system as a whole.