It's also possible some sub EQ would help. If the Rythmik is not breaking a sweat, you might use that PEQ to boost the low end a little in the 20hz range a few db. Or maybe you need the minidsp
. Then you could EQ your sub pretty extensively.
You also might just try running your sub hotter from your receiver output. Turn up the channel level 3 or 4db from where it was measured.
But yeah. The Rythmik fv15hp would be more powerful.
However, I wonder if some of what you were liking with the Klipsch was distortion. See the listening test in this review page : http://www.soundandvisionmag.com/article/shootout-five-mid-price-subwoofers?page=0,4
Seems like the Klipsch loses composure at higher volumes. As they point out, with music, it would sound muddy. With HT usage, the distortion might come across as heavier rumble below 40hz, even though it's not accurate.