Popping from my subwoofer speaker

I replaced the subwoofer amp this year and went from 250 watts RMS to 500 watts and I used the existing speaker wire and 10" speaker. I went out today and checked the system out an I get an occasional obnoxious pop when the stereo is turned up and when going from silence to heavy bass but when the bass is continous the speaker sounds fine. I have a Panasonic KAC-8105D amp and a MTX speaker that has been in the boat for at least 8 years or longer. I have a Kicker 12" sub in a box that I may try and see if that eliminates the popping along with adequate wiring. You stereo dudes (it used to be buffs) have any words of wisdom?

Thanks for the feedback. I have a spare 12" sub on a shelf so I think I will connect that up and see if I have the same problems. I bought the amp last winter on Ebay and I have had good luck with buying there but my luck may have run out on this one.