speakers popping

Ill look into it. I was planning on redoing my whole setup also. I want more bass so plan on replacing the 4 6x9's with CDT 6x9 midrange/subs. Ordering pdx.5 channel amps next week. Yesterday i was checking the settings out on the oz amp thats pushing the 4 speaker highs. the HPF settings were almost turned all the way up. Lowered it down to about 60-80hz and the popping stopped a little bit. still does just not as much and not as loud. Also if i replace the HU do u which brands have the memory card? I like the fact u can download cd's/store them into the HU. I was looking around but dont know what its called... its no the SD card right? Also u think i could try replacing the amps and speakers first then the HU or u think its the HU forsure?

Also thank you very much for the help. I really appreciate it.