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.
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@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.
Hello,
I would get the matching older sub for right now. Everyone says get two matching subs. If you buy the matching sub to your current sub you will have a pair. This should make them both more valuable. I have a pair of the T9’s. I love them. The i or x models are front firing and the older version like mine are down firing with a passive front woofer. I agree if you are buying new subs get the S series for music. I use a home theater pass through on my system. I like that the Rel subs have Speakon and RCA for music and LFE RCA for the movies all separately adjustable. They go down to 28hz so I might add a KEF KF92 sub just for the theater side to go down to 11hz. We will see. Grab the matching sub to yours for now. Wait for a deal on the new REL stuff. 
A matching pair of the newer version REL T/9X, one per channel, would be plenty with your 2-way/6.5" Salk monitor speakers and 60wpc tube amps. Also prefer the forward firing woofer w/bottom firing passive design of the 9x.