Don't take this the wrong way, but DT "Subs" were barely that. It's fairly well documented that they don't perform as well as advertised. Hell, I've even had a DT Salesperson tell me to buy SVS when I was shopping back in 2018!
(I bought neither.)
Regardless, You will enter a completely new world of clean and linear Bass with either the SVS PB 3000 or the Monolith 12s.
I personally think the Monolith 12 will be the better performer if I were to pick, but truth be told they are pretty close.
Definitely do 2.
Regarding your questions.
Either of the options you are considering will destroy the supercubes. It is best if you just accept that those cute little boxes aren't actual Subs.
SVS charges a premium because of their famous customer service and bill of rights... but these are things that still have to be paid for... free shipping 2-ways, upgrade within a year... C'mon... None of that is really free. Rather it is baked into their price. Don't get me wrong, people in the SVS ecosystem love them, and I get it. Not knocking it, but just calling it for what it is.
Until recently, DefTech is known to fudge the specs on their gear. Even your BPs are a lie. the bottom end is rolling off way higher than they advertise. So YES... Modern Subs, again, will far outperform those cute little boxes.
Low frequencies require bigger boxes. This is simple Physics. We all know what happens when you think you can outsmart the natural order of things.
Two Ported Subs like what you are proposing will literally change the way you think about Bass. Good clean Bass is almost subtle. (Until it isn't.
) Poorly designed subwoofers are known to also come with lots of distortion, and that distortion is what most people think of when they think of being annoyed by a subwoofer that is being pushed beyond it's limits.
Strong LF Soundwaves will still rattle things, but in a different way. Many people get their first real Sub and think it isn't doing its job because some of the rattle and distortion they are used to hearing go away. This is what I meant above by "subtle." But as soon as you blow up an entire star system or land a spaceship in your Living Room, a good Subwoofer will be up to the task.
Lastly, we usually recommend multiple Subs, not out of insanity (though that is certainly a part of it) but because they combat acoustic problems in your room that are common to LF Soundwaves. Multiple Subs will play a little louder than a single, true. But you will also benefit from evening out the in-room bass response if you set them up properly. This means from seat to seat, you get more consistent Bass response instead of you getting all the Bass and the person next to you getting nothing.
Hope this helps!
