Infinity RS6? That's a pretty old speaker, but also a true little RS speaker.
What's the wattage on those, 75-100 NEW.. Single bass driver, your hitting the bottom, I bet. I upgraded quite a few Infinity RSs The RS2B, 3Bs, 4B, and 6Bs..
The upgrade I did was change the speaker clip style pocket post to 5 way.
Swap the bass wire to #10 or 12 good copper.
Swap the bass drivers with PE RS HO series drivers.
From good to just wonderful.. You just have to open the hole up a little bit... No more bass issues. Fast and tight...
You can go up another notch by pulling Infinity's stuffing and get REALLY large strand fiberglass and black hole the cabinet. 250.00 or so for everything..The XOs are pretty good, polys they use, last a long time..
There is no parts you can't find for those speakers, good speakers..
They can compete with a lot of today's speakers, for pennies on their dollars..
Regards..