Who are some of elite sub woofers?


Looking to replace Klipsch 12d

So many choices.
awooof
+1 for Rythmik.  Exceptional value, highly adjustable, very musical.  I love my FG12.  With its own adjustability, it integrates seamlessly with my Maggie MMGs through a Parasound P5 preamp. 
For music it is Rel, Rel, Rel.  They're not amazing home theater subs as they don't scare the heck out of you when something explodes on screen.  But they're awesome for music - they don't make the room shake, they make vocals sound real.  I also agree that more than one can even out the room response tremendously..  
Within reason, I have a very healthy budget. I almost fell into the "pay more it must be better" trap. I didn't and bought the SVS's (Ultra SB16) and kept the rest of the money. I am very happy with the pair of SB16's I purchased.

The day you let your ears and not your wallet do the listening is the day you become a man my son. 
Has anybody tried several smaller subs added to a single bigger, more full-range one?  That seems like it'd likely be best bang for the buck.  You could locate the big one where it does best from 20-35hz and have 3 other subs for a smooth response above that.  Low and mid-priced subs can frequently be found deeply discounted.  The reason subs tend to cost a lot is that it's expensive to get loud and deep bass out of a small box without a lot of distortion.  Having multiples would mean the individual subs don't need to be worked near as hard.

I wonder if 6 of these would be better than a single $1,500 sub.  Small, light, cone surface area comparable to a 19.6" driver.  It would certainly smooth out room problems.  If I were going to try something like this I'd run the signal through my equalizer and into a small, cheap power amp to the subs' high level inputs.  I can't imagine it'd be wise to run a low level signal to 6 subs through the amount of wire that would be required.  
https://www.accessories4less.com/make-a-store/item/cabenc1344a/cabasse-santorin-21-m2-8-200-watt-pow...

You could get 5 of these for the same money, probably an even better deal.  Surface area comparable to a 24" driver.  Plus you could brag you've got $8,000 worth of subs.
https://www.accessories4less.com/make-a-store/item/cabenc1082a/cabasse-santorin-25-m2-10-200-watt-po...