VE SV6 Series 2 Thunder Ute Speakers

[madhadder]

Hi all just looking for some advice. I recently brought a 2011 VE SV6 SERIES 2 THUNDER UTE. I installed a sub and mono amp connecting to LOC to factory IQ head unit. It sounds great until I take off quick at lights then it cuts in and out constantly. I did some research and found mostly that everyone was saying to get alpine or kicker 2 way component speakers. I decided to take of door trim and found that the speakers had already been upgraded from previous owner. My question is the speakers he has put in door are KICKER CSC65 coaxial speakers. Then he has put hertz DT 24.3 TWEETERS on dash. Has connected both to the hertz crossover.
IS THIS WRONG BECAUSE THE KICKER SPEAKERS HAVE TWEETERS IN SPEAKER BEING COAXIAL?
IF SO WHAT IS BEST SOLUTION TO FIX? SHOULD I JUST GO OUT AND BUY PROPER 2 WAY COMPONENT SET