My take on subs is its far more about personal sound quality preferences, room, and main speakers than the subs themselves.
The fact is I've enjoyed the db or low level input type subs with certain recordings and times of day I chose to listen. And I did the obsession with measurements, crawl methods, dsp, interconnects, power cables thing. My issue was I could never get a wholly consistent perfectly coherent sound to my main speakers. Different recordings and volume levels always found me making fine adjustments to crossover and gain settings on subs. I'll admit coherency is amongst most important aspects of sound quality for me, this once I had single driver speakers in a bedroom system I used to run. The magical coherency I had with that setup sensitized me forever to incoherency. I've also built my system for max transparency, resolution at relatively low volume listening settings.
Thus far in my admittedly limited listening sessions with the Rel's I've finally found subs that meet my need for coherency, I only hear my Klipschorns. I've no doubt this would not be everyone's cup of tea, they'd be asking where are the subs.
I've been done with subs for years, the Genesis sub and dsp still sits here unused and forlorn. Its only lately that I decided to give the Rel's a try, and this driven far more by the improvements in sound staging people reported vs bass augmentation. My Klipschorns in room response at my listening position certainly aren't bass shy what with my extreme attention to getting maximum seat to the walls, custom birch ply plate at top to get full seal, non stock woofer and crossover. Only missing lowest octives with pipe organs, synth bass.
So, in my case these Rel's exactly what I was looking for, just a bit more reach in lowest freq, and most impressively, the added sound stage ambience, greater recording venue information adds to an already impressive illusion of performers in room that horn speakers do like no other.
In the end each person has to decide for themselves, based on parameters I mentioned above, what subs will work best for themselves. @northman , Only hearing a pair of T7x or 9x in your room and setup will provide the answer for you. I'd only suggest going to another low level input sub with dsp will require another intense setup procedure. If I were you I'd trial a pair of Rel t's and if they don't fit your needs only then move in another direction.
