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
@b_limo Lol! Well, I'm not sure I need to invest in fancy cabinets for a sub, especially since that will increase the weight -- and the wait! And also, if I re-sell, best not to have chosen wood that's too particular. 

By the way, on the servo issue, here's Mcgowan: https://youtu.be/Vk3ti1nTtZ8?t=171
IMO,the discussion of subwoofers in 2 channel audio begins and ends with Rel. Go listen for yourself,its a no brainer
@missioncoonery  I love my current REL. But I have less experience and knowledge than others and the issue of integrating two subs is not just a "go and listen proposition" for me. There's more to it than that, for me. Still, I'm glad you can wrap up the issue so easily for yourself! Congrats on having such confidence in your subs. I hope to get there, myself.
as i see it, the last word in pairing subs to main speakers should be from the maker of the mains - if you have bought into the mains 100% then follow his advice - you will hear what he intends for you to hear

that said, rel has been around a long long time, with many many very satisfied customers... they are true experts and specialists in the field and have not strayed from their central mission, it is hard to imagine their subs, past or present, to be lacking the controls to properly integrate into systems

done right, would imagine either path leads to excellent results
@jjss49  Absolutely right. There's a tendency in discussions to set up an "either/or" when in fact the better answer is "both/and."