I have seen some of the Rythmik stuff, just never heard it. I also think I have a placement issue with my sub. I have bass in certain ares of the room and not so much in others. I saw a video on the audiohics site that covers this topic.
Unfortunately my setup is AV and music. So I have to acomidate both types of listening into the setup.
Nothing "unfortunate" about mixed AV usage! Hell, I play video games, and another member said he "felt bad" using his nice speakers to do the same. But their purpose is to reproduce sound, regardless the origin.
I've heard different opinions, but IF I understand the middle road re: Rythmik, the servo technogy kind of levels the playground because of the calibration/tuning options avialable. One well respected speaker builder I spoke with recommended that I go with sealed 15"Rythmiks, that they would outperform anything else for mixed usage and that ported wasn't really necessary for me. I'm probably 80% music, though and want to get good low extension for pipe organ. *shrugs
I know others here will insist on ported only. I ended up buying Outlaw X-13s during the sale (price was right) -- absolute beasts! And Monoprice Monolith15"s are supposed to have a little higher output than the x-13s. If Budget constrains your choices, check out HSU!
But at the end of the day, Hsu, SVS, Outlaw, Monoprice, and Rythmik are all putting out very good quality product. Just match the subs to what your room volume requires!