Older vs. newer REL subs


Looking for any reports about older vs. newer REL subs.

I have a REL 328 (ca. 2013) which I bought used. It's a good sub.

https://www.hifiplus.com/articles/rel-r-328-subwoofer/

I would like to upgrade to stereo subs and I've found (finally) another REL 328 which would match mine. But, before I drop coin on that, I'm wondering if anyone has had experience comparing their older REL with a newer one. What's changed? What's better, worse, or the same? I'm considering the T7x and T9x lines.

Hoping for apples to apples comparisons, vis a vis driver size, type of sub (e.g. level of product line, sealed vs. ported, music vs. HT etc.) but whatever old vs. newer comparison you have much appreciated. 

Thanks.
128x128hilde45
Hilde45...its not for me to do your homework but ive bought 2 S510 for 2 grand  each delivered from 2 different Rel dealers within the past month, most will discount $250.00 before you even say hello.So with the free shipping they were actually less than 2 grand a pop...if your willing to spend 1500 on a T series sub why wouldn't you go the extra and get a S series (thats very close to their reference level as opposed to their entry line)?
The Ti or Tx series are mot aimed at home theater use.  They do well with that application but they are even better with music. They are the fastest, most responsive subs I’ve heard, by far. They start and stop on a dime.

The S3 SHO was a great sub and a slight upgrade from the T9i but really not worth it Hilde.  A pair of T9i’s or the T9x will already be overkill for you.  Room placement, room acoustics and setup will play a bigger role is good bass response than just randomly plopping down two S3’s or S5’s.

I sold my T9i to a friend and ghat single sub, in his room, has better bass response than any home system I’ve ever heard, RMAF included. Its all about the room, placement and setup once you get to a level like a T9i.  
Heres an analogy.  A trained driver in a 911 can do faster laps than a novice in F1 car.  
On a side note, I picked up my T9i basically brand new (open box) at magnolia for $750 and a S3 SHO (floor model, no box, no grill, no cables, for $1,000).  If I could score a couple of S3 SHO’s for under $3k for the pair I’d look at those as well.  
But anyway you go, T9i, T9X, S3 SHO... a pair will be more than enough and will probably impress the heck out of you.  You can’t go wrong with any of those...
@arafiq 
The KEFs are now gone, and the white sub doesn't go with the aesthetics of my room anymore. So the question now is whether I sell the white T9i and buy a pair of black T9is, or buy a single S/510 for now, and buy a second one next year.

If you end of selling the white T9i....please let me know.
Thanks for the recent comments. It's good to know when one is moving towards overkill in their room. So that could be one reason one would not spend an extra $1,000 for the S series. If there was a good reason to do it and I wanted to spend that money then I would do it. (If anyone would like to pay for my dental work I'd be happy to upgrade even further!

 I can see that in this thread there is a difference of opinion as to whether or not the S series really makes enough of a difference in the room that I have.

Some people believe that buying something of even slightly better quality is always the thing to do. But opportunity costs are real and so it's easy to spend someone else's money. That said if I could get the S series for two grand each and I had a very good acoustical reason to do it, I would do it.
@arafig 
So the question now is whether I sell the white T9i and buy a pair of black T9is, or buy a single S/510 for now, and buy a second one next year.
Buy a pair of black T9s and keep the white one. #swarm