Rythmik F-25's owner here. While I have tried and heard many a sub throughout my audio journey, here are some observations/thoughts I wouldn't mind sharing with you this afternoon.
I prefer front firing, sealed subs.
Adjustments to the mains, as well as to the room are critical.
Raise the height of the subs for optimal impact/ system performance.
Having subs in stereo is much better than just having one sub.
Isolation control is very beneficial.
Never, ever underestimate the impact of IC's and PC's that go to the sub(s).
There is no replacement for displacement.
Low excursion drivers seem to offer tighter visceral impact (not Boom).
IMO, direct servo subs are the most accurate for 2 channel listening. YMMV.
For front firing subs, they must be placed with the same precision as the mains. I am referring to toe in on this one. Not just haphazardly placed. Precision is key here.
These are just my observations. If you want to argue, I will ignore you. That said, if you would like to discuss? I'd be more than happy to engage in a cordial conversation.
Tom