mid range bass

2014 jeep. Replaced oem garbage with kicker separates and coaxials. Using a PPI 640i 5 channel amp, kicker 8" sub. Sub sounds amazing, the clarity has greatly improved and I have a lot more headroom on the volume. I have the gains set around 1/4 up. High pass filter turned on and set to around 210k hz. Anytime I go below 210, the 6.5" speakers start fluttering pretty bad. Sounds awful. I have the factory pods filled with poly fill, I'm wondering if I need to pack it in more? Or take some out? These are my fronts: http://www.crutchfield.com/p_20641S654/Kicker-41KSS654.html?tp=106&awcp=1t1&awcr=47763918083&awdv=t&awkw=41kss654&awmt=p&awnw=g These are my rears: http://www.crutchfield.com/p_2064CS654/Kicker-40CS654.html?tp=95&awcp=1t1&awcr=28870684523&awdv=t&awkw=40cs654&awmt=p&awnw=g This is the amplifier: http://precisionpower.com/store/products/amplifiers/ion/i640-5.html Please help me dial these babies in!

Thanx for the link, I was looking for more physical conditions to cause poor bass. I found the issue and fixed it! The oem jeep enclosures are sealed, they are nice pieces. They are little pods behind the dash that come out and the sound bar on the roll bar. The kicker speakers fit nicely with the adapters .....but, I guess for universal mounting the kicker speakers have 7 holes around the rim that do not include the 4 mounting holes I needed. So in this type of enclosure those 7 holes where like having 7 little ports.lol. High pitched little ports that made it sound like horrible distortion. I removed the speakers from the enclosure and the noise went away, but at higher volumes the speaker was bottoming out and was over extended badly. Used some foam, sealed the holes, sealed the speaker to the enclosure and put them back in, night and day difference. I could finally turn my crossover down to give me a better range between the mods and subwoofer. Sounds great now....for a jeep!