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.
hilde45
Post removed 
@noromance,

I agree. R8 was under speced and sticking it inside a cabinet with no air flow ensured its demise. Most failures of the ST series were solely because of R8.  
When did I say the T series,was for home theater....you have me confused. Im the guy that went from T series to S series in the past 30 days trying to give you first hand advise ....
@missioncoonery My mistake! My apologies. It was not you. I will delete my post!

By the way, I'm in discussions about the S series, now. Thanks for your reports about your experience.
@missioncoonery -- I hope you can shed some light on what aspects of music improved when you moved up from REL's T to S line? My room is 20 x 15, when I called REL customer service they said T9i will be good enough (I already own one) for my room and listening preferences. But a lot of people have told me that there is a distinct advantage when moving up the line regardless of room size. Is it about more bass or an increase in punch and texture or both? TIA.